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832019 Meiosis Krt
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LECTURE 10 MEIOSIS
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INTRODUCTION
Meiosis Definition1 Meiosis is the production of gametes which is a reduction division
which means a diploid gamete produces haploid gametes - from afull complement of chromosomes to halfhellip
2 Two new cells produced during mitosis each have a complete set ofchromosomes (a diploid cell)
3 Meiosis reduces the number of chromosomes by half and produces twohaploid cells from a diploid cell
4 A gamete is a cell that is involved in reproduction
5 Fertilization restores the diploid (two) chromosome number by combining the haploid gametes to the fertilized zygote (A zygote is a diploid cellthat results from the union of two haploid cells)
6
At the end of meiosis gametes are produced four cells - each with half aset of chromosomes - haploid cells7 One set of chromosomes from each parent
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Gametes
Sex chromosomes (X amp Y) Autosomes (non-sex chromosomes)
Somatic cells have 2 sets of autosomes
Gametes have one set of sexchromosomes and one set of autosomes
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Gametes are Haploid
Gametes must have half the genetic material of anormal cell
If the genetic material in the gametes was nothalved when they combined the zygote wouldhave more genetic material than the parents
Meiosis is specialized cell division resulting incells with half the genetic material of the parents
Gametes have exactly one set of chromosomes
this state is called haploid (1n) Regular cells have two sets of chromosomes this
state is called diploid (2n)
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How it works
The chromosomes are duplicated in the Sphase of interphase (just like mitosis)
In Meiosis there are 2 cell divisions
In mitosis the chromosomes line upindividually but in meiosis they line up inhomologous pairs next to each other
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Ideogram of the human chromosomes
p-arm( short )
q-arm( long )
lt= centromere
autosomes
Sex chromosomes
NOR ==gtAcrocenticchromosomes
13 14 1521 22
Xp21
Terminology
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A little more basic terminology
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INTRODUCTION
1 Meiosis is the production of gametes which is areduction division which means a diploid gamete
produces haploid gametes - from a full complementof chromosomes to halfhellip
2 Meiosis reduces the number of chromosomes by halfand produces two haploid cells from a diploid cell
3 A gamete is a cell that is involved in reproduction
4 Fertilization restores the diploid (two) chromosome
number to the zygote (A zygote is a diploid cell thatresults from the union of two haploid cells)
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INTRODUCTION
5 Chromosomes are paired ndash one set are maternal chromosomes the others are paternal
6 Members of the pair are homologouschromosomes
7 There are two divisions in meiosis meiosis I andmeiosis II Each division may include a prophasemetapahse anaphase and telophase
8 As in mitosis the chromosomes are duplicated in the
S phase of interphase9 In meiosis I the members of each homologous pair of
chromosomes are separated into two daughter cells
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INTRODUCTION
10 The chromosomes were duplicated prior to meiosis I so thatthere are two chromotids in each daughter cell
11 In meiosis II chromotids separate into individualchromosomes and enter different haploid daughter cells
12 In Prophase I homologous chromosomes are paired oneof them is from the mother and one from the fatherRemember each chromosome is comprised of twochromatids so that there are four chromatids present at thistime
13 The complex of four chromatids is called a tetrad Thefastening together is called the synapsis In humans thereare 23 tetrads (or 92 chromatids) The number of tetrads isequal to the number of haploid chromosomes
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INTRODUCTION
1 All genes located on a particular chromosomeare linked and will tend to be inheritedtogether in linkage groups
2 Sometimes this doensnrsquot happen duringsynapsis genetic material may be exchangedbetween homologous chromatids by crossing-over Crossing-over produces new
combinations of of genetic materials Plant
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MEIOSIS vs MITOSIS
In mitosis there is one cell division resultingin two daughters with the identical set of
chromosomes as the parent cell
In meiosis there are two cell divisionsproducing four daughters Each cell has the
haploid number of chromosomes that is one
member of each homolgous pair (one setfrom each parent)
So thathellip
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MEIOSIS vs MITOSIS
So thathellip Mitosis - diploid somatic cells yield
diploid somatic cells hellipone cell dividesinto 2 duplicates of itself
Meiosis - Diploid gamete producingcells divide into haploid gameteshelliponecell divides into four cells but they are a
mix of the original Meiosis has two divisions Similar
interphase as in mitosis
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MEIOSIS vs MITOSIS
Prophase I there are two homologouspairs half of each pair is maternal and half ispaternal Each chromosome consists of twochromatids at this time
Synapsis or the pairing of homologous pairsresults in the coming together of four (twomaternal and two paternal) chromatids insteadof just two This is called a tetrad
The number of tetrads equals the haploidnumber of chromosomes (half) Since humans have 46 chromosomes there
are 23 tetrads and a total of 92 chromatids
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MEIOSIS vs MITOSIS
Each cell duplicates the haploid (half ofchromosomes) which combines with the otherhaploids into tetrads
Instead of one homologous pair there are twoThey separate and one of each pair move toends of the cell and then the cell separates
another interphase occurs and the secondseries of meiosis begins
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Stages Of
Meiosis
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Overview
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Steps are similar to mitosis
Duplicated chromosomes (chromatids) arepresent after interphase
The chromatids become paired
One of each pair is contributed by the
organismrsquos mother the other by the father
Because the pairing is of chromatids (2n) there are actually 4 chromosomes present
in what is called a tetrad
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Stages Of Meiosis
1 Meiosis resembles mitosis except that it isactually two divisions not one
2 These divisions are called Meiosis I and Meiosis
II3 Meiosis I results in haploid cells with
chromosomes made up of two chromatids
4 Meiosis II is essentially mitosis on haploid cells
5 Stages of meiosis resemble mitosis with twocritical differences the first in prophase I and thesecond in Metaphase I
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6 The number of tetrads is the haploidnumber of chromosomes (humans have
46 chromosomes so in prophase 1 thereare 92 chromatids and 23 tetrads)
7 Combination process is called synapsis
8 Sometimes during synapsis genetic
material is exchanged betweenchromosomes in process called crossingover
9 All genes located on a particular linkagegroup and tend to be inherited together except for crossing over
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Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
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Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
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Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
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Meiosis
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Meiosis
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Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
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Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
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Meiosis
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Meiosis
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Meiosis
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Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
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Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
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Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
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Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
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In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
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Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
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Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
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Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
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Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
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From Zygote to Embryo
Zygote
2n
Zygote
2n
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Cleavage
From Zygote to Embryo
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Cleavage
From Zygote to Embryo
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Cleavage
From Zygote to Embryo
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Cleavage
From Zygote to Embryo
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Morula
From Zygote to Embryo
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Ch i M i i
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Chromosomes in Meiosis(in a diploid)
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bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
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Crossing over(Recombination)
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Genes in Meiosis
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Meiosis continued
Forms of Chromosomal Non Disjunction
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Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
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Mitosis
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MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
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Mitosis in Action
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Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
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frac12 to child frac12 to child
Looks like mom and dad
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INTRODUCTION
Meiosis Definition1 Meiosis is the production of gametes which is a reduction division
which means a diploid gamete produces haploid gametes - from afull complement of chromosomes to halfhellip
2 Two new cells produced during mitosis each have a complete set ofchromosomes (a diploid cell)
3 Meiosis reduces the number of chromosomes by half and produces twohaploid cells from a diploid cell
4 A gamete is a cell that is involved in reproduction
5 Fertilization restores the diploid (two) chromosome number by combining the haploid gametes to the fertilized zygote (A zygote is a diploid cellthat results from the union of two haploid cells)
6
At the end of meiosis gametes are produced four cells - each with half aset of chromosomes - haploid cells7 One set of chromosomes from each parent
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Gametes
Sex chromosomes (X amp Y) Autosomes (non-sex chromosomes)
Somatic cells have 2 sets of autosomes
Gametes have one set of sexchromosomes and one set of autosomes
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Gametes are Haploid
Gametes must have half the genetic material of anormal cell
If the genetic material in the gametes was nothalved when they combined the zygote wouldhave more genetic material than the parents
Meiosis is specialized cell division resulting incells with half the genetic material of the parents
Gametes have exactly one set of chromosomes
this state is called haploid (1n) Regular cells have two sets of chromosomes this
state is called diploid (2n)
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How it works
The chromosomes are duplicated in the Sphase of interphase (just like mitosis)
In Meiosis there are 2 cell divisions
In mitosis the chromosomes line upindividually but in meiosis they line up inhomologous pairs next to each other
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KRT-2008 6
Ideogram of the human chromosomes
p-arm( short )
q-arm( long )
lt= centromere
autosomes
Sex chromosomes
NOR ==gtAcrocenticchromosomes
13 14 1521 22
Xp21
Terminology
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KRT-2008 7
832019 Meiosis Krt
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KRT-2008 8
A little more basic terminology
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KRT-2008 9
INTRODUCTION
1 Meiosis is the production of gametes which is areduction division which means a diploid gamete
produces haploid gametes - from a full complementof chromosomes to halfhellip
2 Meiosis reduces the number of chromosomes by halfand produces two haploid cells from a diploid cell
3 A gamete is a cell that is involved in reproduction
4 Fertilization restores the diploid (two) chromosome
number to the zygote (A zygote is a diploid cell thatresults from the union of two haploid cells)
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INTRODUCTION
5 Chromosomes are paired ndash one set are maternal chromosomes the others are paternal
6 Members of the pair are homologouschromosomes
7 There are two divisions in meiosis meiosis I andmeiosis II Each division may include a prophasemetapahse anaphase and telophase
8 As in mitosis the chromosomes are duplicated in the
S phase of interphase9 In meiosis I the members of each homologous pair of
chromosomes are separated into two daughter cells
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INTRODUCTION
10 The chromosomes were duplicated prior to meiosis I so thatthere are two chromotids in each daughter cell
11 In meiosis II chromotids separate into individualchromosomes and enter different haploid daughter cells
12 In Prophase I homologous chromosomes are paired oneof them is from the mother and one from the fatherRemember each chromosome is comprised of twochromatids so that there are four chromatids present at thistime
13 The complex of four chromatids is called a tetrad Thefastening together is called the synapsis In humans thereare 23 tetrads (or 92 chromatids) The number of tetrads isequal to the number of haploid chromosomes
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INTRODUCTION
1 All genes located on a particular chromosomeare linked and will tend to be inheritedtogether in linkage groups
2 Sometimes this doensnrsquot happen duringsynapsis genetic material may be exchangedbetween homologous chromatids by crossing-over Crossing-over produces new
combinations of of genetic materials Plant
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MEIOSIS vs MITOSIS
In mitosis there is one cell division resultingin two daughters with the identical set of
chromosomes as the parent cell
In meiosis there are two cell divisionsproducing four daughters Each cell has the
haploid number of chromosomes that is one
member of each homolgous pair (one setfrom each parent)
So thathellip
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MEIOSIS vs MITOSIS
So thathellip Mitosis - diploid somatic cells yield
diploid somatic cells hellipone cell dividesinto 2 duplicates of itself
Meiosis - Diploid gamete producingcells divide into haploid gameteshelliponecell divides into four cells but they are a
mix of the original Meiosis has two divisions Similar
interphase as in mitosis
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MEIOSIS vs MITOSIS
Prophase I there are two homologouspairs half of each pair is maternal and half ispaternal Each chromosome consists of twochromatids at this time
Synapsis or the pairing of homologous pairsresults in the coming together of four (twomaternal and two paternal) chromatids insteadof just two This is called a tetrad
The number of tetrads equals the haploidnumber of chromosomes (half) Since humans have 46 chromosomes there
are 23 tetrads and a total of 92 chromatids
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MEIOSIS vs MITOSIS
Each cell duplicates the haploid (half ofchromosomes) which combines with the otherhaploids into tetrads
Instead of one homologous pair there are twoThey separate and one of each pair move toends of the cell and then the cell separates
another interphase occurs and the secondseries of meiosis begins
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Stages Of
Meiosis
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Overview
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Steps are similar to mitosis
Duplicated chromosomes (chromatids) arepresent after interphase
The chromatids become paired
One of each pair is contributed by the
organismrsquos mother the other by the father
Because the pairing is of chromatids (2n) there are actually 4 chromosomes present
in what is called a tetrad
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KRT-2008 20
Stages Of Meiosis
1 Meiosis resembles mitosis except that it isactually two divisions not one
2 These divisions are called Meiosis I and Meiosis
II3 Meiosis I results in haploid cells with
chromosomes made up of two chromatids
4 Meiosis II is essentially mitosis on haploid cells
5 Stages of meiosis resemble mitosis with twocritical differences the first in prophase I and thesecond in Metaphase I
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KRT-2008 21
6 The number of tetrads is the haploidnumber of chromosomes (humans have
46 chromosomes so in prophase 1 thereare 92 chromatids and 23 tetrads)
7 Combination process is called synapsis
8 Sometimes during synapsis genetic
material is exchanged betweenchromosomes in process called crossingover
9 All genes located on a particular linkagegroup and tend to be inherited together except for crossing over
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Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
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Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
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Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
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Meiosis
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Meiosis
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Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
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Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
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Meiosis
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Meiosis
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Meiosis
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Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
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KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
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KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
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Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
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In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
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Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
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Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
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Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
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From Zygote to Embryo
Zygote
2n
Zygote
2n
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Cleavage
From Zygote to Embryo
832019 Meiosis Krt
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Cleavage
From Zygote to Embryo
832019 Meiosis Krt
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Cleavage
From Zygote to Embryo
832019 Meiosis Krt
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Cleavage
From Zygote to Embryo
832019 Meiosis Krt
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Morula
From Zygote to Embryo
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Ch i M i i
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KRT-2008 48
Chromosomes in Meiosis(in a diploid)
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bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
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Crossing over(Recombination)
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Genes in Meiosis
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Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
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Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
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MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
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Mitosis in Action
832019 Meiosis Krt
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Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
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Gametes
Sex chromosomes (X amp Y) Autosomes (non-sex chromosomes)
Somatic cells have 2 sets of autosomes
Gametes have one set of sexchromosomes and one set of autosomes
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KRT-2008 4
Gametes are Haploid
Gametes must have half the genetic material of anormal cell
If the genetic material in the gametes was nothalved when they combined the zygote wouldhave more genetic material than the parents
Meiosis is specialized cell division resulting incells with half the genetic material of the parents
Gametes have exactly one set of chromosomes
this state is called haploid (1n) Regular cells have two sets of chromosomes this
state is called diploid (2n)
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How it works
The chromosomes are duplicated in the Sphase of interphase (just like mitosis)
In Meiosis there are 2 cell divisions
In mitosis the chromosomes line upindividually but in meiosis they line up inhomologous pairs next to each other
832019 Meiosis Krt
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KRT-2008 6
Ideogram of the human chromosomes
p-arm( short )
q-arm( long )
lt= centromere
autosomes
Sex chromosomes
NOR ==gtAcrocenticchromosomes
13 14 1521 22
Xp21
Terminology
832019 Meiosis Krt
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KRT-2008 7
832019 Meiosis Krt
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KRT-2008 8
A little more basic terminology
832019 Meiosis Krt
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KRT-2008 9
INTRODUCTION
1 Meiosis is the production of gametes which is areduction division which means a diploid gamete
produces haploid gametes - from a full complementof chromosomes to halfhellip
2 Meiosis reduces the number of chromosomes by halfand produces two haploid cells from a diploid cell
3 A gamete is a cell that is involved in reproduction
4 Fertilization restores the diploid (two) chromosome
number to the zygote (A zygote is a diploid cell thatresults from the union of two haploid cells)
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KRT-2008 10
INTRODUCTION
5 Chromosomes are paired ndash one set are maternal chromosomes the others are paternal
6 Members of the pair are homologouschromosomes
7 There are two divisions in meiosis meiosis I andmeiosis II Each division may include a prophasemetapahse anaphase and telophase
8 As in mitosis the chromosomes are duplicated in the
S phase of interphase9 In meiosis I the members of each homologous pair of
chromosomes are separated into two daughter cells
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KRT-2008 11
INTRODUCTION
10 The chromosomes were duplicated prior to meiosis I so thatthere are two chromotids in each daughter cell
11 In meiosis II chromotids separate into individualchromosomes and enter different haploid daughter cells
12 In Prophase I homologous chromosomes are paired oneof them is from the mother and one from the fatherRemember each chromosome is comprised of twochromatids so that there are four chromatids present at thistime
13 The complex of four chromatids is called a tetrad Thefastening together is called the synapsis In humans thereare 23 tetrads (or 92 chromatids) The number of tetrads isequal to the number of haploid chromosomes
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KRT-2008 12
INTRODUCTION
1 All genes located on a particular chromosomeare linked and will tend to be inheritedtogether in linkage groups
2 Sometimes this doensnrsquot happen duringsynapsis genetic material may be exchangedbetween homologous chromatids by crossing-over Crossing-over produces new
combinations of of genetic materials Plant
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1360
KRT-2008 13
MEIOSIS vs MITOSIS
In mitosis there is one cell division resultingin two daughters with the identical set of
chromosomes as the parent cell
In meiosis there are two cell divisionsproducing four daughters Each cell has the
haploid number of chromosomes that is one
member of each homolgous pair (one setfrom each parent)
So thathellip
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KRT-2008 14
MEIOSIS vs MITOSIS
So thathellip Mitosis - diploid somatic cells yield
diploid somatic cells hellipone cell dividesinto 2 duplicates of itself
Meiosis - Diploid gamete producingcells divide into haploid gameteshelliponecell divides into four cells but they are a
mix of the original Meiosis has two divisions Similar
interphase as in mitosis
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KRT-2008 15
MEIOSIS vs MITOSIS
Prophase I there are two homologouspairs half of each pair is maternal and half ispaternal Each chromosome consists of twochromatids at this time
Synapsis or the pairing of homologous pairsresults in the coming together of four (twomaternal and two paternal) chromatids insteadof just two This is called a tetrad
The number of tetrads equals the haploidnumber of chromosomes (half) Since humans have 46 chromosomes there
are 23 tetrads and a total of 92 chromatids
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KRT-2008 16
MEIOSIS vs MITOSIS
Each cell duplicates the haploid (half ofchromosomes) which combines with the otherhaploids into tetrads
Instead of one homologous pair there are twoThey separate and one of each pair move toends of the cell and then the cell separates
another interphase occurs and the secondseries of meiosis begins
832019 Meiosis Krt
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KRT-2008 17
Stages Of
Meiosis
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KRT-2008 18
Overview
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Steps are similar to mitosis
Duplicated chromosomes (chromatids) arepresent after interphase
The chromatids become paired
One of each pair is contributed by the
organismrsquos mother the other by the father
Because the pairing is of chromatids (2n) there are actually 4 chromosomes present
in what is called a tetrad
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KRT-2008 20
Stages Of Meiosis
1 Meiosis resembles mitosis except that it isactually two divisions not one
2 These divisions are called Meiosis I and Meiosis
II3 Meiosis I results in haploid cells with
chromosomes made up of two chromatids
4 Meiosis II is essentially mitosis on haploid cells
5 Stages of meiosis resemble mitosis with twocritical differences the first in prophase I and thesecond in Metaphase I
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KRT-2008 21
6 The number of tetrads is the haploidnumber of chromosomes (humans have
46 chromosomes so in prophase 1 thereare 92 chromatids and 23 tetrads)
7 Combination process is called synapsis
8 Sometimes during synapsis genetic
material is exchanged betweenchromosomes in process called crossingover
9 All genes located on a particular linkagegroup and tend to be inherited together except for crossing over
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KRT-2008 22
Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
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KRT-2008 23
Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
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KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
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KRT-2008 25
Meiosis
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KRT-2008 26
Meiosis
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KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
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KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
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KRT-2008 29
Meiosis
832019 Meiosis Krt
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KRT-2008 30
Meiosis
832019 Meiosis Krt
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KRT-2008 31
Meiosis
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KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
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KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
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KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
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Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
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Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
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Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
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From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
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Cleavage
From Zygote to Embryo
832019 Meiosis Krt
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Cleavage
From Zygote to Embryo
832019 Meiosis Krt
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Cleavage
From Zygote to Embryo
832019 Meiosis Krt
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Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
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Ch i M i i
832019 Meiosis Krt
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KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
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832019 Meiosis Krt
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bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
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Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
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Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
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MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 460
KRT-2008 4
Gametes are Haploid
Gametes must have half the genetic material of anormal cell
If the genetic material in the gametes was nothalved when they combined the zygote wouldhave more genetic material than the parents
Meiosis is specialized cell division resulting incells with half the genetic material of the parents
Gametes have exactly one set of chromosomes
this state is called haploid (1n) Regular cells have two sets of chromosomes this
state is called diploid (2n)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 560
How it works
The chromosomes are duplicated in the Sphase of interphase (just like mitosis)
In Meiosis there are 2 cell divisions
In mitosis the chromosomes line upindividually but in meiosis they line up inhomologous pairs next to each other
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 660
KRT-2008 6
Ideogram of the human chromosomes
p-arm( short )
q-arm( long )
lt= centromere
autosomes
Sex chromosomes
NOR ==gtAcrocenticchromosomes
13 14 1521 22
Xp21
Terminology
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 760
KRT-2008 7
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 860
KRT-2008 8
A little more basic terminology
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 960
KRT-2008 9
INTRODUCTION
1 Meiosis is the production of gametes which is areduction division which means a diploid gamete
produces haploid gametes - from a full complementof chromosomes to halfhellip
2 Meiosis reduces the number of chromosomes by halfand produces two haploid cells from a diploid cell
3 A gamete is a cell that is involved in reproduction
4 Fertilization restores the diploid (two) chromosome
number to the zygote (A zygote is a diploid cell thatresults from the union of two haploid cells)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1060
KRT-2008 10
INTRODUCTION
5 Chromosomes are paired ndash one set are maternal chromosomes the others are paternal
6 Members of the pair are homologouschromosomes
7 There are two divisions in meiosis meiosis I andmeiosis II Each division may include a prophasemetapahse anaphase and telophase
8 As in mitosis the chromosomes are duplicated in the
S phase of interphase9 In meiosis I the members of each homologous pair of
chromosomes are separated into two daughter cells
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1160
KRT-2008 11
INTRODUCTION
10 The chromosomes were duplicated prior to meiosis I so thatthere are two chromotids in each daughter cell
11 In meiosis II chromotids separate into individualchromosomes and enter different haploid daughter cells
12 In Prophase I homologous chromosomes are paired oneof them is from the mother and one from the fatherRemember each chromosome is comprised of twochromatids so that there are four chromatids present at thistime
13 The complex of four chromatids is called a tetrad Thefastening together is called the synapsis In humans thereare 23 tetrads (or 92 chromatids) The number of tetrads isequal to the number of haploid chromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1260
KRT-2008 12
INTRODUCTION
1 All genes located on a particular chromosomeare linked and will tend to be inheritedtogether in linkage groups
2 Sometimes this doensnrsquot happen duringsynapsis genetic material may be exchangedbetween homologous chromatids by crossing-over Crossing-over produces new
combinations of of genetic materials Plant
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1360
KRT-2008 13
MEIOSIS vs MITOSIS
In mitosis there is one cell division resultingin two daughters with the identical set of
chromosomes as the parent cell
In meiosis there are two cell divisionsproducing four daughters Each cell has the
haploid number of chromosomes that is one
member of each homolgous pair (one setfrom each parent)
So thathellip
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1460
KRT-2008 14
MEIOSIS vs MITOSIS
So thathellip Mitosis - diploid somatic cells yield
diploid somatic cells hellipone cell dividesinto 2 duplicates of itself
Meiosis - Diploid gamete producingcells divide into haploid gameteshelliponecell divides into four cells but they are a
mix of the original Meiosis has two divisions Similar
interphase as in mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1560
KRT-2008 15
MEIOSIS vs MITOSIS
Prophase I there are two homologouspairs half of each pair is maternal and half ispaternal Each chromosome consists of twochromatids at this time
Synapsis or the pairing of homologous pairsresults in the coming together of four (twomaternal and two paternal) chromatids insteadof just two This is called a tetrad
The number of tetrads equals the haploidnumber of chromosomes (half) Since humans have 46 chromosomes there
are 23 tetrads and a total of 92 chromatids
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1660
KRT-2008 16
MEIOSIS vs MITOSIS
Each cell duplicates the haploid (half ofchromosomes) which combines with the otherhaploids into tetrads
Instead of one homologous pair there are twoThey separate and one of each pair move toends of the cell and then the cell separates
another interphase occurs and the secondseries of meiosis begins
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1760
KRT-2008 17
Stages Of
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1860
KRT-2008 18
Overview
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1960
Steps are similar to mitosis
Duplicated chromosomes (chromatids) arepresent after interphase
The chromatids become paired
One of each pair is contributed by the
organismrsquos mother the other by the father
Because the pairing is of chromatids (2n) there are actually 4 chromosomes present
in what is called a tetrad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2060
KRT-2008 20
Stages Of Meiosis
1 Meiosis resembles mitosis except that it isactually two divisions not one
2 These divisions are called Meiosis I and Meiosis
II3 Meiosis I results in haploid cells with
chromosomes made up of two chromatids
4 Meiosis II is essentially mitosis on haploid cells
5 Stages of meiosis resemble mitosis with twocritical differences the first in prophase I and thesecond in Metaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2160
KRT-2008 21
6 The number of tetrads is the haploidnumber of chromosomes (humans have
46 chromosomes so in prophase 1 thereare 92 chromatids and 23 tetrads)
7 Combination process is called synapsis
8 Sometimes during synapsis genetic
material is exchanged betweenchromosomes in process called crossingover
9 All genes located on a particular linkagegroup and tend to be inherited together except for crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2260
KRT-2008 22
Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2360
KRT-2008 23
Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2460
KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2660
KRT-2008 26
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
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KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 560
How it works
The chromosomes are duplicated in the Sphase of interphase (just like mitosis)
In Meiosis there are 2 cell divisions
In mitosis the chromosomes line upindividually but in meiosis they line up inhomologous pairs next to each other
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 660
KRT-2008 6
Ideogram of the human chromosomes
p-arm( short )
q-arm( long )
lt= centromere
autosomes
Sex chromosomes
NOR ==gtAcrocenticchromosomes
13 14 1521 22
Xp21
Terminology
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 760
KRT-2008 7
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 860
KRT-2008 8
A little more basic terminology
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 960
KRT-2008 9
INTRODUCTION
1 Meiosis is the production of gametes which is areduction division which means a diploid gamete
produces haploid gametes - from a full complementof chromosomes to halfhellip
2 Meiosis reduces the number of chromosomes by halfand produces two haploid cells from a diploid cell
3 A gamete is a cell that is involved in reproduction
4 Fertilization restores the diploid (two) chromosome
number to the zygote (A zygote is a diploid cell thatresults from the union of two haploid cells)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1060
KRT-2008 10
INTRODUCTION
5 Chromosomes are paired ndash one set are maternal chromosomes the others are paternal
6 Members of the pair are homologouschromosomes
7 There are two divisions in meiosis meiosis I andmeiosis II Each division may include a prophasemetapahse anaphase and telophase
8 As in mitosis the chromosomes are duplicated in the
S phase of interphase9 In meiosis I the members of each homologous pair of
chromosomes are separated into two daughter cells
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1160
KRT-2008 11
INTRODUCTION
10 The chromosomes were duplicated prior to meiosis I so thatthere are two chromotids in each daughter cell
11 In meiosis II chromotids separate into individualchromosomes and enter different haploid daughter cells
12 In Prophase I homologous chromosomes are paired oneof them is from the mother and one from the fatherRemember each chromosome is comprised of twochromatids so that there are four chromatids present at thistime
13 The complex of four chromatids is called a tetrad Thefastening together is called the synapsis In humans thereare 23 tetrads (or 92 chromatids) The number of tetrads isequal to the number of haploid chromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1260
KRT-2008 12
INTRODUCTION
1 All genes located on a particular chromosomeare linked and will tend to be inheritedtogether in linkage groups
2 Sometimes this doensnrsquot happen duringsynapsis genetic material may be exchangedbetween homologous chromatids by crossing-over Crossing-over produces new
combinations of of genetic materials Plant
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1360
KRT-2008 13
MEIOSIS vs MITOSIS
In mitosis there is one cell division resultingin two daughters with the identical set of
chromosomes as the parent cell
In meiosis there are two cell divisionsproducing four daughters Each cell has the
haploid number of chromosomes that is one
member of each homolgous pair (one setfrom each parent)
So thathellip
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1460
KRT-2008 14
MEIOSIS vs MITOSIS
So thathellip Mitosis - diploid somatic cells yield
diploid somatic cells hellipone cell dividesinto 2 duplicates of itself
Meiosis - Diploid gamete producingcells divide into haploid gameteshelliponecell divides into four cells but they are a
mix of the original Meiosis has two divisions Similar
interphase as in mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1560
KRT-2008 15
MEIOSIS vs MITOSIS
Prophase I there are two homologouspairs half of each pair is maternal and half ispaternal Each chromosome consists of twochromatids at this time
Synapsis or the pairing of homologous pairsresults in the coming together of four (twomaternal and two paternal) chromatids insteadof just two This is called a tetrad
The number of tetrads equals the haploidnumber of chromosomes (half) Since humans have 46 chromosomes there
are 23 tetrads and a total of 92 chromatids
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1660
KRT-2008 16
MEIOSIS vs MITOSIS
Each cell duplicates the haploid (half ofchromosomes) which combines with the otherhaploids into tetrads
Instead of one homologous pair there are twoThey separate and one of each pair move toends of the cell and then the cell separates
another interphase occurs and the secondseries of meiosis begins
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1760
KRT-2008 17
Stages Of
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1860
KRT-2008 18
Overview
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1960
Steps are similar to mitosis
Duplicated chromosomes (chromatids) arepresent after interphase
The chromatids become paired
One of each pair is contributed by the
organismrsquos mother the other by the father
Because the pairing is of chromatids (2n) there are actually 4 chromosomes present
in what is called a tetrad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2060
KRT-2008 20
Stages Of Meiosis
1 Meiosis resembles mitosis except that it isactually two divisions not one
2 These divisions are called Meiosis I and Meiosis
II3 Meiosis I results in haploid cells with
chromosomes made up of two chromatids
4 Meiosis II is essentially mitosis on haploid cells
5 Stages of meiosis resemble mitosis with twocritical differences the first in prophase I and thesecond in Metaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2160
KRT-2008 21
6 The number of tetrads is the haploidnumber of chromosomes (humans have
46 chromosomes so in prophase 1 thereare 92 chromatids and 23 tetrads)
7 Combination process is called synapsis
8 Sometimes during synapsis genetic
material is exchanged betweenchromosomes in process called crossingover
9 All genes located on a particular linkagegroup and tend to be inherited together except for crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2260
KRT-2008 22
Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2360
KRT-2008 23
Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2460
KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2660
KRT-2008 26
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 660
KRT-2008 6
Ideogram of the human chromosomes
p-arm( short )
q-arm( long )
lt= centromere
autosomes
Sex chromosomes
NOR ==gtAcrocenticchromosomes
13 14 1521 22
Xp21
Terminology
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 760
KRT-2008 7
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 860
KRT-2008 8
A little more basic terminology
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 960
KRT-2008 9
INTRODUCTION
1 Meiosis is the production of gametes which is areduction division which means a diploid gamete
produces haploid gametes - from a full complementof chromosomes to halfhellip
2 Meiosis reduces the number of chromosomes by halfand produces two haploid cells from a diploid cell
3 A gamete is a cell that is involved in reproduction
4 Fertilization restores the diploid (two) chromosome
number to the zygote (A zygote is a diploid cell thatresults from the union of two haploid cells)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1060
KRT-2008 10
INTRODUCTION
5 Chromosomes are paired ndash one set are maternal chromosomes the others are paternal
6 Members of the pair are homologouschromosomes
7 There are two divisions in meiosis meiosis I andmeiosis II Each division may include a prophasemetapahse anaphase and telophase
8 As in mitosis the chromosomes are duplicated in the
S phase of interphase9 In meiosis I the members of each homologous pair of
chromosomes are separated into two daughter cells
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1160
KRT-2008 11
INTRODUCTION
10 The chromosomes were duplicated prior to meiosis I so thatthere are two chromotids in each daughter cell
11 In meiosis II chromotids separate into individualchromosomes and enter different haploid daughter cells
12 In Prophase I homologous chromosomes are paired oneof them is from the mother and one from the fatherRemember each chromosome is comprised of twochromatids so that there are four chromatids present at thistime
13 The complex of four chromatids is called a tetrad Thefastening together is called the synapsis In humans thereare 23 tetrads (or 92 chromatids) The number of tetrads isequal to the number of haploid chromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1260
KRT-2008 12
INTRODUCTION
1 All genes located on a particular chromosomeare linked and will tend to be inheritedtogether in linkage groups
2 Sometimes this doensnrsquot happen duringsynapsis genetic material may be exchangedbetween homologous chromatids by crossing-over Crossing-over produces new
combinations of of genetic materials Plant
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1360
KRT-2008 13
MEIOSIS vs MITOSIS
In mitosis there is one cell division resultingin two daughters with the identical set of
chromosomes as the parent cell
In meiosis there are two cell divisionsproducing four daughters Each cell has the
haploid number of chromosomes that is one
member of each homolgous pair (one setfrom each parent)
So thathellip
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1460
KRT-2008 14
MEIOSIS vs MITOSIS
So thathellip Mitosis - diploid somatic cells yield
diploid somatic cells hellipone cell dividesinto 2 duplicates of itself
Meiosis - Diploid gamete producingcells divide into haploid gameteshelliponecell divides into four cells but they are a
mix of the original Meiosis has two divisions Similar
interphase as in mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1560
KRT-2008 15
MEIOSIS vs MITOSIS
Prophase I there are two homologouspairs half of each pair is maternal and half ispaternal Each chromosome consists of twochromatids at this time
Synapsis or the pairing of homologous pairsresults in the coming together of four (twomaternal and two paternal) chromatids insteadof just two This is called a tetrad
The number of tetrads equals the haploidnumber of chromosomes (half) Since humans have 46 chromosomes there
are 23 tetrads and a total of 92 chromatids
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1660
KRT-2008 16
MEIOSIS vs MITOSIS
Each cell duplicates the haploid (half ofchromosomes) which combines with the otherhaploids into tetrads
Instead of one homologous pair there are twoThey separate and one of each pair move toends of the cell and then the cell separates
another interphase occurs and the secondseries of meiosis begins
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1760
KRT-2008 17
Stages Of
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1860
KRT-2008 18
Overview
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1960
Steps are similar to mitosis
Duplicated chromosomes (chromatids) arepresent after interphase
The chromatids become paired
One of each pair is contributed by the
organismrsquos mother the other by the father
Because the pairing is of chromatids (2n) there are actually 4 chromosomes present
in what is called a tetrad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2060
KRT-2008 20
Stages Of Meiosis
1 Meiosis resembles mitosis except that it isactually two divisions not one
2 These divisions are called Meiosis I and Meiosis
II3 Meiosis I results in haploid cells with
chromosomes made up of two chromatids
4 Meiosis II is essentially mitosis on haploid cells
5 Stages of meiosis resemble mitosis with twocritical differences the first in prophase I and thesecond in Metaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2160
KRT-2008 21
6 The number of tetrads is the haploidnumber of chromosomes (humans have
46 chromosomes so in prophase 1 thereare 92 chromatids and 23 tetrads)
7 Combination process is called synapsis
8 Sometimes during synapsis genetic
material is exchanged betweenchromosomes in process called crossingover
9 All genes located on a particular linkagegroup and tend to be inherited together except for crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2260
KRT-2008 22
Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2360
KRT-2008 23
Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2460
KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2660
KRT-2008 26
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 760
KRT-2008 7
832019 Meiosis Krt
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KRT-2008 8
A little more basic terminology
832019 Meiosis Krt
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KRT-2008 9
INTRODUCTION
1 Meiosis is the production of gametes which is areduction division which means a diploid gamete
produces haploid gametes - from a full complementof chromosomes to halfhellip
2 Meiosis reduces the number of chromosomes by halfand produces two haploid cells from a diploid cell
3 A gamete is a cell that is involved in reproduction
4 Fertilization restores the diploid (two) chromosome
number to the zygote (A zygote is a diploid cell thatresults from the union of two haploid cells)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1060
KRT-2008 10
INTRODUCTION
5 Chromosomes are paired ndash one set are maternal chromosomes the others are paternal
6 Members of the pair are homologouschromosomes
7 There are two divisions in meiosis meiosis I andmeiosis II Each division may include a prophasemetapahse anaphase and telophase
8 As in mitosis the chromosomes are duplicated in the
S phase of interphase9 In meiosis I the members of each homologous pair of
chromosomes are separated into two daughter cells
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1160
KRT-2008 11
INTRODUCTION
10 The chromosomes were duplicated prior to meiosis I so thatthere are two chromotids in each daughter cell
11 In meiosis II chromotids separate into individualchromosomes and enter different haploid daughter cells
12 In Prophase I homologous chromosomes are paired oneof them is from the mother and one from the fatherRemember each chromosome is comprised of twochromatids so that there are four chromatids present at thistime
13 The complex of four chromatids is called a tetrad Thefastening together is called the synapsis In humans thereare 23 tetrads (or 92 chromatids) The number of tetrads isequal to the number of haploid chromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1260
KRT-2008 12
INTRODUCTION
1 All genes located on a particular chromosomeare linked and will tend to be inheritedtogether in linkage groups
2 Sometimes this doensnrsquot happen duringsynapsis genetic material may be exchangedbetween homologous chromatids by crossing-over Crossing-over produces new
combinations of of genetic materials Plant
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1360
KRT-2008 13
MEIOSIS vs MITOSIS
In mitosis there is one cell division resultingin two daughters with the identical set of
chromosomes as the parent cell
In meiosis there are two cell divisionsproducing four daughters Each cell has the
haploid number of chromosomes that is one
member of each homolgous pair (one setfrom each parent)
So thathellip
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1460
KRT-2008 14
MEIOSIS vs MITOSIS
So thathellip Mitosis - diploid somatic cells yield
diploid somatic cells hellipone cell dividesinto 2 duplicates of itself
Meiosis - Diploid gamete producingcells divide into haploid gameteshelliponecell divides into four cells but they are a
mix of the original Meiosis has two divisions Similar
interphase as in mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1560
KRT-2008 15
MEIOSIS vs MITOSIS
Prophase I there are two homologouspairs half of each pair is maternal and half ispaternal Each chromosome consists of twochromatids at this time
Synapsis or the pairing of homologous pairsresults in the coming together of four (twomaternal and two paternal) chromatids insteadof just two This is called a tetrad
The number of tetrads equals the haploidnumber of chromosomes (half) Since humans have 46 chromosomes there
are 23 tetrads and a total of 92 chromatids
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1660
KRT-2008 16
MEIOSIS vs MITOSIS
Each cell duplicates the haploid (half ofchromosomes) which combines with the otherhaploids into tetrads
Instead of one homologous pair there are twoThey separate and one of each pair move toends of the cell and then the cell separates
another interphase occurs and the secondseries of meiosis begins
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1760
KRT-2008 17
Stages Of
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1860
KRT-2008 18
Overview
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1960
Steps are similar to mitosis
Duplicated chromosomes (chromatids) arepresent after interphase
The chromatids become paired
One of each pair is contributed by the
organismrsquos mother the other by the father
Because the pairing is of chromatids (2n) there are actually 4 chromosomes present
in what is called a tetrad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2060
KRT-2008 20
Stages Of Meiosis
1 Meiosis resembles mitosis except that it isactually two divisions not one
2 These divisions are called Meiosis I and Meiosis
II3 Meiosis I results in haploid cells with
chromosomes made up of two chromatids
4 Meiosis II is essentially mitosis on haploid cells
5 Stages of meiosis resemble mitosis with twocritical differences the first in prophase I and thesecond in Metaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2160
KRT-2008 21
6 The number of tetrads is the haploidnumber of chromosomes (humans have
46 chromosomes so in prophase 1 thereare 92 chromatids and 23 tetrads)
7 Combination process is called synapsis
8 Sometimes during synapsis genetic
material is exchanged betweenchromosomes in process called crossingover
9 All genes located on a particular linkagegroup and tend to be inherited together except for crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2260
KRT-2008 22
Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2360
KRT-2008 23
Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2460
KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2660
KRT-2008 26
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 860
KRT-2008 8
A little more basic terminology
832019 Meiosis Krt
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KRT-2008 9
INTRODUCTION
1 Meiosis is the production of gametes which is areduction division which means a diploid gamete
produces haploid gametes - from a full complementof chromosomes to halfhellip
2 Meiosis reduces the number of chromosomes by halfand produces two haploid cells from a diploid cell
3 A gamete is a cell that is involved in reproduction
4 Fertilization restores the diploid (two) chromosome
number to the zygote (A zygote is a diploid cell thatresults from the union of two haploid cells)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1060
KRT-2008 10
INTRODUCTION
5 Chromosomes are paired ndash one set are maternal chromosomes the others are paternal
6 Members of the pair are homologouschromosomes
7 There are two divisions in meiosis meiosis I andmeiosis II Each division may include a prophasemetapahse anaphase and telophase
8 As in mitosis the chromosomes are duplicated in the
S phase of interphase9 In meiosis I the members of each homologous pair of
chromosomes are separated into two daughter cells
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1160
KRT-2008 11
INTRODUCTION
10 The chromosomes were duplicated prior to meiosis I so thatthere are two chromotids in each daughter cell
11 In meiosis II chromotids separate into individualchromosomes and enter different haploid daughter cells
12 In Prophase I homologous chromosomes are paired oneof them is from the mother and one from the fatherRemember each chromosome is comprised of twochromatids so that there are four chromatids present at thistime
13 The complex of four chromatids is called a tetrad Thefastening together is called the synapsis In humans thereare 23 tetrads (or 92 chromatids) The number of tetrads isequal to the number of haploid chromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1260
KRT-2008 12
INTRODUCTION
1 All genes located on a particular chromosomeare linked and will tend to be inheritedtogether in linkage groups
2 Sometimes this doensnrsquot happen duringsynapsis genetic material may be exchangedbetween homologous chromatids by crossing-over Crossing-over produces new
combinations of of genetic materials Plant
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1360
KRT-2008 13
MEIOSIS vs MITOSIS
In mitosis there is one cell division resultingin two daughters with the identical set of
chromosomes as the parent cell
In meiosis there are two cell divisionsproducing four daughters Each cell has the
haploid number of chromosomes that is one
member of each homolgous pair (one setfrom each parent)
So thathellip
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1460
KRT-2008 14
MEIOSIS vs MITOSIS
So thathellip Mitosis - diploid somatic cells yield
diploid somatic cells hellipone cell dividesinto 2 duplicates of itself
Meiosis - Diploid gamete producingcells divide into haploid gameteshelliponecell divides into four cells but they are a
mix of the original Meiosis has two divisions Similar
interphase as in mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1560
KRT-2008 15
MEIOSIS vs MITOSIS
Prophase I there are two homologouspairs half of each pair is maternal and half ispaternal Each chromosome consists of twochromatids at this time
Synapsis or the pairing of homologous pairsresults in the coming together of four (twomaternal and two paternal) chromatids insteadof just two This is called a tetrad
The number of tetrads equals the haploidnumber of chromosomes (half) Since humans have 46 chromosomes there
are 23 tetrads and a total of 92 chromatids
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1660
KRT-2008 16
MEIOSIS vs MITOSIS
Each cell duplicates the haploid (half ofchromosomes) which combines with the otherhaploids into tetrads
Instead of one homologous pair there are twoThey separate and one of each pair move toends of the cell and then the cell separates
another interphase occurs and the secondseries of meiosis begins
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1760
KRT-2008 17
Stages Of
Meiosis
832019 Meiosis Krt
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KRT-2008 18
Overview
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1960
Steps are similar to mitosis
Duplicated chromosomes (chromatids) arepresent after interphase
The chromatids become paired
One of each pair is contributed by the
organismrsquos mother the other by the father
Because the pairing is of chromatids (2n) there are actually 4 chromosomes present
in what is called a tetrad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2060
KRT-2008 20
Stages Of Meiosis
1 Meiosis resembles mitosis except that it isactually two divisions not one
2 These divisions are called Meiosis I and Meiosis
II3 Meiosis I results in haploid cells with
chromosomes made up of two chromatids
4 Meiosis II is essentially mitosis on haploid cells
5 Stages of meiosis resemble mitosis with twocritical differences the first in prophase I and thesecond in Metaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2160
KRT-2008 21
6 The number of tetrads is the haploidnumber of chromosomes (humans have
46 chromosomes so in prophase 1 thereare 92 chromatids and 23 tetrads)
7 Combination process is called synapsis
8 Sometimes during synapsis genetic
material is exchanged betweenchromosomes in process called crossingover
9 All genes located on a particular linkagegroup and tend to be inherited together except for crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2260
KRT-2008 22
Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2360
KRT-2008 23
Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2460
KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
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KRT-2008 26
Meiosis
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KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
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KRT-2008 29
Meiosis
832019 Meiosis Krt
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KRT-2008 30
Meiosis
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KRT-2008 31
Meiosis
832019 Meiosis Krt
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KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
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KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
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KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
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KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
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832019 Meiosis Krt
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bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
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Mitosis
832019 Meiosis Krt
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MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 960
KRT-2008 9
INTRODUCTION
1 Meiosis is the production of gametes which is areduction division which means a diploid gamete
produces haploid gametes - from a full complementof chromosomes to halfhellip
2 Meiosis reduces the number of chromosomes by halfand produces two haploid cells from a diploid cell
3 A gamete is a cell that is involved in reproduction
4 Fertilization restores the diploid (two) chromosome
number to the zygote (A zygote is a diploid cell thatresults from the union of two haploid cells)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1060
KRT-2008 10
INTRODUCTION
5 Chromosomes are paired ndash one set are maternal chromosomes the others are paternal
6 Members of the pair are homologouschromosomes
7 There are two divisions in meiosis meiosis I andmeiosis II Each division may include a prophasemetapahse anaphase and telophase
8 As in mitosis the chromosomes are duplicated in the
S phase of interphase9 In meiosis I the members of each homologous pair of
chromosomes are separated into two daughter cells
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1160
KRT-2008 11
INTRODUCTION
10 The chromosomes were duplicated prior to meiosis I so thatthere are two chromotids in each daughter cell
11 In meiosis II chromotids separate into individualchromosomes and enter different haploid daughter cells
12 In Prophase I homologous chromosomes are paired oneof them is from the mother and one from the fatherRemember each chromosome is comprised of twochromatids so that there are four chromatids present at thistime
13 The complex of four chromatids is called a tetrad Thefastening together is called the synapsis In humans thereare 23 tetrads (or 92 chromatids) The number of tetrads isequal to the number of haploid chromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1260
KRT-2008 12
INTRODUCTION
1 All genes located on a particular chromosomeare linked and will tend to be inheritedtogether in linkage groups
2 Sometimes this doensnrsquot happen duringsynapsis genetic material may be exchangedbetween homologous chromatids by crossing-over Crossing-over produces new
combinations of of genetic materials Plant
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1360
KRT-2008 13
MEIOSIS vs MITOSIS
In mitosis there is one cell division resultingin two daughters with the identical set of
chromosomes as the parent cell
In meiosis there are two cell divisionsproducing four daughters Each cell has the
haploid number of chromosomes that is one
member of each homolgous pair (one setfrom each parent)
So thathellip
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1460
KRT-2008 14
MEIOSIS vs MITOSIS
So thathellip Mitosis - diploid somatic cells yield
diploid somatic cells hellipone cell dividesinto 2 duplicates of itself
Meiosis - Diploid gamete producingcells divide into haploid gameteshelliponecell divides into four cells but they are a
mix of the original Meiosis has two divisions Similar
interphase as in mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1560
KRT-2008 15
MEIOSIS vs MITOSIS
Prophase I there are two homologouspairs half of each pair is maternal and half ispaternal Each chromosome consists of twochromatids at this time
Synapsis or the pairing of homologous pairsresults in the coming together of four (twomaternal and two paternal) chromatids insteadof just two This is called a tetrad
The number of tetrads equals the haploidnumber of chromosomes (half) Since humans have 46 chromosomes there
are 23 tetrads and a total of 92 chromatids
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1660
KRT-2008 16
MEIOSIS vs MITOSIS
Each cell duplicates the haploid (half ofchromosomes) which combines with the otherhaploids into tetrads
Instead of one homologous pair there are twoThey separate and one of each pair move toends of the cell and then the cell separates
another interphase occurs and the secondseries of meiosis begins
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1760
KRT-2008 17
Stages Of
Meiosis
832019 Meiosis Krt
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KRT-2008 18
Overview
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1960
Steps are similar to mitosis
Duplicated chromosomes (chromatids) arepresent after interphase
The chromatids become paired
One of each pair is contributed by the
organismrsquos mother the other by the father
Because the pairing is of chromatids (2n) there are actually 4 chromosomes present
in what is called a tetrad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2060
KRT-2008 20
Stages Of Meiosis
1 Meiosis resembles mitosis except that it isactually two divisions not one
2 These divisions are called Meiosis I and Meiosis
II3 Meiosis I results in haploid cells with
chromosomes made up of two chromatids
4 Meiosis II is essentially mitosis on haploid cells
5 Stages of meiosis resemble mitosis with twocritical differences the first in prophase I and thesecond in Metaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2160
KRT-2008 21
6 The number of tetrads is the haploidnumber of chromosomes (humans have
46 chromosomes so in prophase 1 thereare 92 chromatids and 23 tetrads)
7 Combination process is called synapsis
8 Sometimes during synapsis genetic
material is exchanged betweenchromosomes in process called crossingover
9 All genes located on a particular linkagegroup and tend to be inherited together except for crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2260
KRT-2008 22
Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2360
KRT-2008 23
Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2460
KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
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KRT-2008 26
Meiosis
832019 Meiosis Krt
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KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
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KRT-2008 30
Meiosis
832019 Meiosis Krt
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KRT-2008 31
Meiosis
832019 Meiosis Krt
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KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
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KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1060
KRT-2008 10
INTRODUCTION
5 Chromosomes are paired ndash one set are maternal chromosomes the others are paternal
6 Members of the pair are homologouschromosomes
7 There are two divisions in meiosis meiosis I andmeiosis II Each division may include a prophasemetapahse anaphase and telophase
8 As in mitosis the chromosomes are duplicated in the
S phase of interphase9 In meiosis I the members of each homologous pair of
chromosomes are separated into two daughter cells
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1160
KRT-2008 11
INTRODUCTION
10 The chromosomes were duplicated prior to meiosis I so thatthere are two chromotids in each daughter cell
11 In meiosis II chromotids separate into individualchromosomes and enter different haploid daughter cells
12 In Prophase I homologous chromosomes are paired oneof them is from the mother and one from the fatherRemember each chromosome is comprised of twochromatids so that there are four chromatids present at thistime
13 The complex of four chromatids is called a tetrad Thefastening together is called the synapsis In humans thereare 23 tetrads (or 92 chromatids) The number of tetrads isequal to the number of haploid chromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1260
KRT-2008 12
INTRODUCTION
1 All genes located on a particular chromosomeare linked and will tend to be inheritedtogether in linkage groups
2 Sometimes this doensnrsquot happen duringsynapsis genetic material may be exchangedbetween homologous chromatids by crossing-over Crossing-over produces new
combinations of of genetic materials Plant
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1360
KRT-2008 13
MEIOSIS vs MITOSIS
In mitosis there is one cell division resultingin two daughters with the identical set of
chromosomes as the parent cell
In meiosis there are two cell divisionsproducing four daughters Each cell has the
haploid number of chromosomes that is one
member of each homolgous pair (one setfrom each parent)
So thathellip
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1460
KRT-2008 14
MEIOSIS vs MITOSIS
So thathellip Mitosis - diploid somatic cells yield
diploid somatic cells hellipone cell dividesinto 2 duplicates of itself
Meiosis - Diploid gamete producingcells divide into haploid gameteshelliponecell divides into four cells but they are a
mix of the original Meiosis has two divisions Similar
interphase as in mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1560
KRT-2008 15
MEIOSIS vs MITOSIS
Prophase I there are two homologouspairs half of each pair is maternal and half ispaternal Each chromosome consists of twochromatids at this time
Synapsis or the pairing of homologous pairsresults in the coming together of four (twomaternal and two paternal) chromatids insteadof just two This is called a tetrad
The number of tetrads equals the haploidnumber of chromosomes (half) Since humans have 46 chromosomes there
are 23 tetrads and a total of 92 chromatids
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1660
KRT-2008 16
MEIOSIS vs MITOSIS
Each cell duplicates the haploid (half ofchromosomes) which combines with the otherhaploids into tetrads
Instead of one homologous pair there are twoThey separate and one of each pair move toends of the cell and then the cell separates
another interphase occurs and the secondseries of meiosis begins
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1760
KRT-2008 17
Stages Of
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1860
KRT-2008 18
Overview
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1960
Steps are similar to mitosis
Duplicated chromosomes (chromatids) arepresent after interphase
The chromatids become paired
One of each pair is contributed by the
organismrsquos mother the other by the father
Because the pairing is of chromatids (2n) there are actually 4 chromosomes present
in what is called a tetrad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2060
KRT-2008 20
Stages Of Meiosis
1 Meiosis resembles mitosis except that it isactually two divisions not one
2 These divisions are called Meiosis I and Meiosis
II3 Meiosis I results in haploid cells with
chromosomes made up of two chromatids
4 Meiosis II is essentially mitosis on haploid cells
5 Stages of meiosis resemble mitosis with twocritical differences the first in prophase I and thesecond in Metaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2160
KRT-2008 21
6 The number of tetrads is the haploidnumber of chromosomes (humans have
46 chromosomes so in prophase 1 thereare 92 chromatids and 23 tetrads)
7 Combination process is called synapsis
8 Sometimes during synapsis genetic
material is exchanged betweenchromosomes in process called crossingover
9 All genes located on a particular linkagegroup and tend to be inherited together except for crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2260
KRT-2008 22
Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2360
KRT-2008 23
Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2460
KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2660
KRT-2008 26
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1160
KRT-2008 11
INTRODUCTION
10 The chromosomes were duplicated prior to meiosis I so thatthere are two chromotids in each daughter cell
11 In meiosis II chromotids separate into individualchromosomes and enter different haploid daughter cells
12 In Prophase I homologous chromosomes are paired oneof them is from the mother and one from the fatherRemember each chromosome is comprised of twochromatids so that there are four chromatids present at thistime
13 The complex of four chromatids is called a tetrad Thefastening together is called the synapsis In humans thereare 23 tetrads (or 92 chromatids) The number of tetrads isequal to the number of haploid chromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1260
KRT-2008 12
INTRODUCTION
1 All genes located on a particular chromosomeare linked and will tend to be inheritedtogether in linkage groups
2 Sometimes this doensnrsquot happen duringsynapsis genetic material may be exchangedbetween homologous chromatids by crossing-over Crossing-over produces new
combinations of of genetic materials Plant
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1360
KRT-2008 13
MEIOSIS vs MITOSIS
In mitosis there is one cell division resultingin two daughters with the identical set of
chromosomes as the parent cell
In meiosis there are two cell divisionsproducing four daughters Each cell has the
haploid number of chromosomes that is one
member of each homolgous pair (one setfrom each parent)
So thathellip
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1460
KRT-2008 14
MEIOSIS vs MITOSIS
So thathellip Mitosis - diploid somatic cells yield
diploid somatic cells hellipone cell dividesinto 2 duplicates of itself
Meiosis - Diploid gamete producingcells divide into haploid gameteshelliponecell divides into four cells but they are a
mix of the original Meiosis has two divisions Similar
interphase as in mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1560
KRT-2008 15
MEIOSIS vs MITOSIS
Prophase I there are two homologouspairs half of each pair is maternal and half ispaternal Each chromosome consists of twochromatids at this time
Synapsis or the pairing of homologous pairsresults in the coming together of four (twomaternal and two paternal) chromatids insteadof just two This is called a tetrad
The number of tetrads equals the haploidnumber of chromosomes (half) Since humans have 46 chromosomes there
are 23 tetrads and a total of 92 chromatids
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1660
KRT-2008 16
MEIOSIS vs MITOSIS
Each cell duplicates the haploid (half ofchromosomes) which combines with the otherhaploids into tetrads
Instead of one homologous pair there are twoThey separate and one of each pair move toends of the cell and then the cell separates
another interphase occurs and the secondseries of meiosis begins
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1760
KRT-2008 17
Stages Of
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1860
KRT-2008 18
Overview
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1960
Steps are similar to mitosis
Duplicated chromosomes (chromatids) arepresent after interphase
The chromatids become paired
One of each pair is contributed by the
organismrsquos mother the other by the father
Because the pairing is of chromatids (2n) there are actually 4 chromosomes present
in what is called a tetrad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2060
KRT-2008 20
Stages Of Meiosis
1 Meiosis resembles mitosis except that it isactually two divisions not one
2 These divisions are called Meiosis I and Meiosis
II3 Meiosis I results in haploid cells with
chromosomes made up of two chromatids
4 Meiosis II is essentially mitosis on haploid cells
5 Stages of meiosis resemble mitosis with twocritical differences the first in prophase I and thesecond in Metaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2160
KRT-2008 21
6 The number of tetrads is the haploidnumber of chromosomes (humans have
46 chromosomes so in prophase 1 thereare 92 chromatids and 23 tetrads)
7 Combination process is called synapsis
8 Sometimes during synapsis genetic
material is exchanged betweenchromosomes in process called crossingover
9 All genes located on a particular linkagegroup and tend to be inherited together except for crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2260
KRT-2008 22
Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2360
KRT-2008 23
Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2460
KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2660
KRT-2008 26
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1260
KRT-2008 12
INTRODUCTION
1 All genes located on a particular chromosomeare linked and will tend to be inheritedtogether in linkage groups
2 Sometimes this doensnrsquot happen duringsynapsis genetic material may be exchangedbetween homologous chromatids by crossing-over Crossing-over produces new
combinations of of genetic materials Plant
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1360
KRT-2008 13
MEIOSIS vs MITOSIS
In mitosis there is one cell division resultingin two daughters with the identical set of
chromosomes as the parent cell
In meiosis there are two cell divisionsproducing four daughters Each cell has the
haploid number of chromosomes that is one
member of each homolgous pair (one setfrom each parent)
So thathellip
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1460
KRT-2008 14
MEIOSIS vs MITOSIS
So thathellip Mitosis - diploid somatic cells yield
diploid somatic cells hellipone cell dividesinto 2 duplicates of itself
Meiosis - Diploid gamete producingcells divide into haploid gameteshelliponecell divides into four cells but they are a
mix of the original Meiosis has two divisions Similar
interphase as in mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1560
KRT-2008 15
MEIOSIS vs MITOSIS
Prophase I there are two homologouspairs half of each pair is maternal and half ispaternal Each chromosome consists of twochromatids at this time
Synapsis or the pairing of homologous pairsresults in the coming together of four (twomaternal and two paternal) chromatids insteadof just two This is called a tetrad
The number of tetrads equals the haploidnumber of chromosomes (half) Since humans have 46 chromosomes there
are 23 tetrads and a total of 92 chromatids
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1660
KRT-2008 16
MEIOSIS vs MITOSIS
Each cell duplicates the haploid (half ofchromosomes) which combines with the otherhaploids into tetrads
Instead of one homologous pair there are twoThey separate and one of each pair move toends of the cell and then the cell separates
another interphase occurs and the secondseries of meiosis begins
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1760
KRT-2008 17
Stages Of
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1860
KRT-2008 18
Overview
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1960
Steps are similar to mitosis
Duplicated chromosomes (chromatids) arepresent after interphase
The chromatids become paired
One of each pair is contributed by the
organismrsquos mother the other by the father
Because the pairing is of chromatids (2n) there are actually 4 chromosomes present
in what is called a tetrad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2060
KRT-2008 20
Stages Of Meiosis
1 Meiosis resembles mitosis except that it isactually two divisions not one
2 These divisions are called Meiosis I and Meiosis
II3 Meiosis I results in haploid cells with
chromosomes made up of two chromatids
4 Meiosis II is essentially mitosis on haploid cells
5 Stages of meiosis resemble mitosis with twocritical differences the first in prophase I and thesecond in Metaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2160
KRT-2008 21
6 The number of tetrads is the haploidnumber of chromosomes (humans have
46 chromosomes so in prophase 1 thereare 92 chromatids and 23 tetrads)
7 Combination process is called synapsis
8 Sometimes during synapsis genetic
material is exchanged betweenchromosomes in process called crossingover
9 All genes located on a particular linkagegroup and tend to be inherited together except for crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2260
KRT-2008 22
Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2360
KRT-2008 23
Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2460
KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2660
KRT-2008 26
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1360
KRT-2008 13
MEIOSIS vs MITOSIS
In mitosis there is one cell division resultingin two daughters with the identical set of
chromosomes as the parent cell
In meiosis there are two cell divisionsproducing four daughters Each cell has the
haploid number of chromosomes that is one
member of each homolgous pair (one setfrom each parent)
So thathellip
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1460
KRT-2008 14
MEIOSIS vs MITOSIS
So thathellip Mitosis - diploid somatic cells yield
diploid somatic cells hellipone cell dividesinto 2 duplicates of itself
Meiosis - Diploid gamete producingcells divide into haploid gameteshelliponecell divides into four cells but they are a
mix of the original Meiosis has two divisions Similar
interphase as in mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1560
KRT-2008 15
MEIOSIS vs MITOSIS
Prophase I there are two homologouspairs half of each pair is maternal and half ispaternal Each chromosome consists of twochromatids at this time
Synapsis or the pairing of homologous pairsresults in the coming together of four (twomaternal and two paternal) chromatids insteadof just two This is called a tetrad
The number of tetrads equals the haploidnumber of chromosomes (half) Since humans have 46 chromosomes there
are 23 tetrads and a total of 92 chromatids
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1660
KRT-2008 16
MEIOSIS vs MITOSIS
Each cell duplicates the haploid (half ofchromosomes) which combines with the otherhaploids into tetrads
Instead of one homologous pair there are twoThey separate and one of each pair move toends of the cell and then the cell separates
another interphase occurs and the secondseries of meiosis begins
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1760
KRT-2008 17
Stages Of
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1860
KRT-2008 18
Overview
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1960
Steps are similar to mitosis
Duplicated chromosomes (chromatids) arepresent after interphase
The chromatids become paired
One of each pair is contributed by the
organismrsquos mother the other by the father
Because the pairing is of chromatids (2n) there are actually 4 chromosomes present
in what is called a tetrad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2060
KRT-2008 20
Stages Of Meiosis
1 Meiosis resembles mitosis except that it isactually two divisions not one
2 These divisions are called Meiosis I and Meiosis
II3 Meiosis I results in haploid cells with
chromosomes made up of two chromatids
4 Meiosis II is essentially mitosis on haploid cells
5 Stages of meiosis resemble mitosis with twocritical differences the first in prophase I and thesecond in Metaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2160
KRT-2008 21
6 The number of tetrads is the haploidnumber of chromosomes (humans have
46 chromosomes so in prophase 1 thereare 92 chromatids and 23 tetrads)
7 Combination process is called synapsis
8 Sometimes during synapsis genetic
material is exchanged betweenchromosomes in process called crossingover
9 All genes located on a particular linkagegroup and tend to be inherited together except for crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2260
KRT-2008 22
Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2360
KRT-2008 23
Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2460
KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2660
KRT-2008 26
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1460
KRT-2008 14
MEIOSIS vs MITOSIS
So thathellip Mitosis - diploid somatic cells yield
diploid somatic cells hellipone cell dividesinto 2 duplicates of itself
Meiosis - Diploid gamete producingcells divide into haploid gameteshelliponecell divides into four cells but they are a
mix of the original Meiosis has two divisions Similar
interphase as in mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1560
KRT-2008 15
MEIOSIS vs MITOSIS
Prophase I there are two homologouspairs half of each pair is maternal and half ispaternal Each chromosome consists of twochromatids at this time
Synapsis or the pairing of homologous pairsresults in the coming together of four (twomaternal and two paternal) chromatids insteadof just two This is called a tetrad
The number of tetrads equals the haploidnumber of chromosomes (half) Since humans have 46 chromosomes there
are 23 tetrads and a total of 92 chromatids
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1660
KRT-2008 16
MEIOSIS vs MITOSIS
Each cell duplicates the haploid (half ofchromosomes) which combines with the otherhaploids into tetrads
Instead of one homologous pair there are twoThey separate and one of each pair move toends of the cell and then the cell separates
another interphase occurs and the secondseries of meiosis begins
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1760
KRT-2008 17
Stages Of
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1860
KRT-2008 18
Overview
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1960
Steps are similar to mitosis
Duplicated chromosomes (chromatids) arepresent after interphase
The chromatids become paired
One of each pair is contributed by the
organismrsquos mother the other by the father
Because the pairing is of chromatids (2n) there are actually 4 chromosomes present
in what is called a tetrad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2060
KRT-2008 20
Stages Of Meiosis
1 Meiosis resembles mitosis except that it isactually two divisions not one
2 These divisions are called Meiosis I and Meiosis
II3 Meiosis I results in haploid cells with
chromosomes made up of two chromatids
4 Meiosis II is essentially mitosis on haploid cells
5 Stages of meiosis resemble mitosis with twocritical differences the first in prophase I and thesecond in Metaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2160
KRT-2008 21
6 The number of tetrads is the haploidnumber of chromosomes (humans have
46 chromosomes so in prophase 1 thereare 92 chromatids and 23 tetrads)
7 Combination process is called synapsis
8 Sometimes during synapsis genetic
material is exchanged betweenchromosomes in process called crossingover
9 All genes located on a particular linkagegroup and tend to be inherited together except for crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2260
KRT-2008 22
Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2360
KRT-2008 23
Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2460
KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2660
KRT-2008 26
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1560
KRT-2008 15
MEIOSIS vs MITOSIS
Prophase I there are two homologouspairs half of each pair is maternal and half ispaternal Each chromosome consists of twochromatids at this time
Synapsis or the pairing of homologous pairsresults in the coming together of four (twomaternal and two paternal) chromatids insteadof just two This is called a tetrad
The number of tetrads equals the haploidnumber of chromosomes (half) Since humans have 46 chromosomes there
are 23 tetrads and a total of 92 chromatids
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1660
KRT-2008 16
MEIOSIS vs MITOSIS
Each cell duplicates the haploid (half ofchromosomes) which combines with the otherhaploids into tetrads
Instead of one homologous pair there are twoThey separate and one of each pair move toends of the cell and then the cell separates
another interphase occurs and the secondseries of meiosis begins
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1760
KRT-2008 17
Stages Of
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1860
KRT-2008 18
Overview
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1960
Steps are similar to mitosis
Duplicated chromosomes (chromatids) arepresent after interphase
The chromatids become paired
One of each pair is contributed by the
organismrsquos mother the other by the father
Because the pairing is of chromatids (2n) there are actually 4 chromosomes present
in what is called a tetrad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2060
KRT-2008 20
Stages Of Meiosis
1 Meiosis resembles mitosis except that it isactually two divisions not one
2 These divisions are called Meiosis I and Meiosis
II3 Meiosis I results in haploid cells with
chromosomes made up of two chromatids
4 Meiosis II is essentially mitosis on haploid cells
5 Stages of meiosis resemble mitosis with twocritical differences the first in prophase I and thesecond in Metaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2160
KRT-2008 21
6 The number of tetrads is the haploidnumber of chromosomes (humans have
46 chromosomes so in prophase 1 thereare 92 chromatids and 23 tetrads)
7 Combination process is called synapsis
8 Sometimes during synapsis genetic
material is exchanged betweenchromosomes in process called crossingover
9 All genes located on a particular linkagegroup and tend to be inherited together except for crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2260
KRT-2008 22
Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2360
KRT-2008 23
Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2460
KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2660
KRT-2008 26
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1660
KRT-2008 16
MEIOSIS vs MITOSIS
Each cell duplicates the haploid (half ofchromosomes) which combines with the otherhaploids into tetrads
Instead of one homologous pair there are twoThey separate and one of each pair move toends of the cell and then the cell separates
another interphase occurs and the secondseries of meiosis begins
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1760
KRT-2008 17
Stages Of
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1860
KRT-2008 18
Overview
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1960
Steps are similar to mitosis
Duplicated chromosomes (chromatids) arepresent after interphase
The chromatids become paired
One of each pair is contributed by the
organismrsquos mother the other by the father
Because the pairing is of chromatids (2n) there are actually 4 chromosomes present
in what is called a tetrad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2060
KRT-2008 20
Stages Of Meiosis
1 Meiosis resembles mitosis except that it isactually two divisions not one
2 These divisions are called Meiosis I and Meiosis
II3 Meiosis I results in haploid cells with
chromosomes made up of two chromatids
4 Meiosis II is essentially mitosis on haploid cells
5 Stages of meiosis resemble mitosis with twocritical differences the first in prophase I and thesecond in Metaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2160
KRT-2008 21
6 The number of tetrads is the haploidnumber of chromosomes (humans have
46 chromosomes so in prophase 1 thereare 92 chromatids and 23 tetrads)
7 Combination process is called synapsis
8 Sometimes during synapsis genetic
material is exchanged betweenchromosomes in process called crossingover
9 All genes located on a particular linkagegroup and tend to be inherited together except for crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2260
KRT-2008 22
Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2360
KRT-2008 23
Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2460
KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2660
KRT-2008 26
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1760
KRT-2008 17
Stages Of
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1860
KRT-2008 18
Overview
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1960
Steps are similar to mitosis
Duplicated chromosomes (chromatids) arepresent after interphase
The chromatids become paired
One of each pair is contributed by the
organismrsquos mother the other by the father
Because the pairing is of chromatids (2n) there are actually 4 chromosomes present
in what is called a tetrad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2060
KRT-2008 20
Stages Of Meiosis
1 Meiosis resembles mitosis except that it isactually two divisions not one
2 These divisions are called Meiosis I and Meiosis
II3 Meiosis I results in haploid cells with
chromosomes made up of two chromatids
4 Meiosis II is essentially mitosis on haploid cells
5 Stages of meiosis resemble mitosis with twocritical differences the first in prophase I and thesecond in Metaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2160
KRT-2008 21
6 The number of tetrads is the haploidnumber of chromosomes (humans have
46 chromosomes so in prophase 1 thereare 92 chromatids and 23 tetrads)
7 Combination process is called synapsis
8 Sometimes during synapsis genetic
material is exchanged betweenchromosomes in process called crossingover
9 All genes located on a particular linkagegroup and tend to be inherited together except for crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2260
KRT-2008 22
Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2360
KRT-2008 23
Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2460
KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2660
KRT-2008 26
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1860
KRT-2008 18
Overview
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1960
Steps are similar to mitosis
Duplicated chromosomes (chromatids) arepresent after interphase
The chromatids become paired
One of each pair is contributed by the
organismrsquos mother the other by the father
Because the pairing is of chromatids (2n) there are actually 4 chromosomes present
in what is called a tetrad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2060
KRT-2008 20
Stages Of Meiosis
1 Meiosis resembles mitosis except that it isactually two divisions not one
2 These divisions are called Meiosis I and Meiosis
II3 Meiosis I results in haploid cells with
chromosomes made up of two chromatids
4 Meiosis II is essentially mitosis on haploid cells
5 Stages of meiosis resemble mitosis with twocritical differences the first in prophase I and thesecond in Metaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2160
KRT-2008 21
6 The number of tetrads is the haploidnumber of chromosomes (humans have
46 chromosomes so in prophase 1 thereare 92 chromatids and 23 tetrads)
7 Combination process is called synapsis
8 Sometimes during synapsis genetic
material is exchanged betweenchromosomes in process called crossingover
9 All genes located on a particular linkagegroup and tend to be inherited together except for crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2260
KRT-2008 22
Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2360
KRT-2008 23
Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2460
KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2660
KRT-2008 26
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 1960
Steps are similar to mitosis
Duplicated chromosomes (chromatids) arepresent after interphase
The chromatids become paired
One of each pair is contributed by the
organismrsquos mother the other by the father
Because the pairing is of chromatids (2n) there are actually 4 chromosomes present
in what is called a tetrad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2060
KRT-2008 20
Stages Of Meiosis
1 Meiosis resembles mitosis except that it isactually two divisions not one
2 These divisions are called Meiosis I and Meiosis
II3 Meiosis I results in haploid cells with
chromosomes made up of two chromatids
4 Meiosis II is essentially mitosis on haploid cells
5 Stages of meiosis resemble mitosis with twocritical differences the first in prophase I and thesecond in Metaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2160
KRT-2008 21
6 The number of tetrads is the haploidnumber of chromosomes (humans have
46 chromosomes so in prophase 1 thereare 92 chromatids and 23 tetrads)
7 Combination process is called synapsis
8 Sometimes during synapsis genetic
material is exchanged betweenchromosomes in process called crossingover
9 All genes located on a particular linkagegroup and tend to be inherited together except for crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2260
KRT-2008 22
Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2360
KRT-2008 23
Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2460
KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2660
KRT-2008 26
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2060
KRT-2008 20
Stages Of Meiosis
1 Meiosis resembles mitosis except that it isactually two divisions not one
2 These divisions are called Meiosis I and Meiosis
II3 Meiosis I results in haploid cells with
chromosomes made up of two chromatids
4 Meiosis II is essentially mitosis on haploid cells
5 Stages of meiosis resemble mitosis with twocritical differences the first in prophase I and thesecond in Metaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2160
KRT-2008 21
6 The number of tetrads is the haploidnumber of chromosomes (humans have
46 chromosomes so in prophase 1 thereare 92 chromatids and 23 tetrads)
7 Combination process is called synapsis
8 Sometimes during synapsis genetic
material is exchanged betweenchromosomes in process called crossingover
9 All genes located on a particular linkagegroup and tend to be inherited together except for crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2260
KRT-2008 22
Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2360
KRT-2008 23
Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2460
KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2660
KRT-2008 26
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2160
KRT-2008 21
6 The number of tetrads is the haploidnumber of chromosomes (humans have
46 chromosomes so in prophase 1 thereare 92 chromatids and 23 tetrads)
7 Combination process is called synapsis
8 Sometimes during synapsis genetic
material is exchanged betweenchromosomes in process called crossingover
9 All genes located on a particular linkagegroup and tend to be inherited together except for crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2260
KRT-2008 22
Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2360
KRT-2008 23
Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2460
KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2660
KRT-2008 26
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2260
KRT-2008 22
Stages Of Meiosis - Meiosis I
Prophase I - The beginning phase
DNA which was unraveled (=terurai) andspread all over the nucleus is condensedand packaged
Homologous chromosomes (each made oftwo identical chromatids) come togetherand form tetrads (4 chromatids)
Crossing over in which chromatids withintetrads exchange genetic material occurs
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2360
KRT-2008 23
Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2460
KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2660
KRT-2008 26
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2360
KRT-2008 23
Stages Of Meiosis - Meiosis I
Metaphase I - Middle stage Tetrads line up along the equator of the cell and
sister chromatids orient toward opposite poles
Anaphase 1 Tetrads separate and move toward poles but
chromatids still connected by centromere
One copy of each chromosome still composed oftwo chromatids moves to each pole of the cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2460
KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2660
KRT-2008 26
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2460
KRT-2008 24
Stages Of Meiosis - Meiosis I
Telophase I - End stage New nuclear membranes are formed around
the chromosomes and cytokinesis
(cytoplasm division) occurs resulting in twohaploid daughter cells
At the end of telophase 1 there are twodoubled chromosomes at each end of cell
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2660
KRT-2008 26
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2560
KRT-2008 25
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2660
KRT-2008 26
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2660
KRT-2008 26
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2760
KRT-2008 27
Stages Of Meiosis - Meiosis II
Prophase II Cells do not typically go into interphase between meiosis I
and II thus chromosomes are already condensed
Metaphase II
Chromosomes line up at the equator of the two haploidcells produced in meiosis I
Because homologous pairs line up in Metaphase 1 there isa 5050 chance of which one of each pair will go to eachpole
In humans with 23 chromosomes any couple would have223 x 223 chance of different possible children (about 1 in70 trillion and this doesnrsquot account for crossing over)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2860
KRT-2008 28
Stages Of Meiosis - Meiosis II
Anaphase II - Chromosomes made up of twochromatids split to make chromosomes withone chromatid which migrate to the poles of
the cells Centromeres split in anaphase 2 andchromatids move to poles
Telophase II - Cytokinesis and reformation ofthe nuclear membrane in haploid cells eachwith one set of chromosomes made of onechromatid At the end of telophase there isone chromatid at each end (haploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 2960
KRT-2008 29
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3060
KRT-2008 30
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3160
KRT-2008 31
Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3260
KRT-2008 32
Interphase
Mother cell Stages Of Meiosis Meiosis I
Meiosis II
Prophase ITetrad formation
crossing over
Metaphase I
Telophase I
Prophase I
CondensingChromosomes
Anaphase I
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3360
KRT-2008 33
Telophase I Stages Of MeiosisMeiosis II
Metaphase II
Anaphase II
Telophase II
The products of mitosis ar
2 diploid cells with
identical chromosomes
The products of meiosis are 4haploid cells each with a unique set
of chromosomes
Prophase II
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3460
KRT-2008 34
Prophase ITetrad formation
crossing over
Crossing Over
Anaphase I
Telophase II
Metaphase I
Telophase IBecause of crossing over every
gamete receives a unique set of
genetic information
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3560
Replication
Chromosomes Chromatids and
Centromeres
Centromere
Chromosome arm
Chromosomearm
Identicalchromatid
Chromatid
Anaphase
A packaged
chromosome
Two identicalchromosomes
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3660
In The Beginning Two
1 Humans and many other complex multi-celledorganisms incorporate genetic recombination intheir reproduction
2 Reproduction in which there is a re-mixing of the
genetic material is called sexual reproduction3 Two cells a sperm and an egg unite to form a
zygote the single cell from which the organismdevelops
4 Meiosis is the process of producing sperm andeggs (gametes)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3760
Egg
1n
Haploid
nucleus
Fertilization Results In A Diploid
Zygote
Sperm
2nHaploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3860
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 3960
Sperm
2n
Fertilization Results In A DiploidZygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4060
Sperm
2n
Fertilization Results In ADiploid Zygote
Egg
1n
Haploid
nucleus
Haploid
nucleus
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4160
From Zygote to Embryo
Zygote
2n
Zygote
2n
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4260
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4360
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4460
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4560
Cleavage
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4660
Morula
From Zygote to Embryo
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4760
Ch i M i i
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4860
KRT-2008 48
Chromosomes in Meiosis(in a diploid)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 4960
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5060
bull Occurs duringprophase I
bull Chiasma (pl
chiasmata)indicatewherechromosomeshaveexchangedgeneticmaterial
Crossing over
Crossing over
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5160
Crossing over(Recombination)
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5260
Genes in Meiosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5360
Meiosis continued
Forms of Chromosomal Non Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5460
Euploidy addition or loss of complete sets of chromosomes
Triploidy complete extra set of chromosomes - 69caused by fertilization of an egg by more than onesperm or an egg that failed to divide
Tetraploidy complete extra diploid set of chromosome - 92caused by a failure of the first zygotic division
Aneuploidy gain or loss of a single chromosomefailure in meioses (usually)
Monosomies loss of a chromosome ndash Turner syndromeautosomal monosomies are lethalsex monosomies survive
Trisomies gain of a chromosome- Down Tri 13 Tri 18 Klinefelter
Forms of Chromosomal Non-Disjunction
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5560
Mitosis
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5660
MitosisInterphase
bull cells not dividing (majority of time)bull chromosomes are decondensed - synthesizing
productsbull all the cells DNA is duplicated ndash chromatid duplicates
Prophasebull chromatin condenses to form chromosomesbull spindle apparatus formsbull separation of sister chromatids into 2 daughter cells
Metaphase
bull spindle to the centromeresbull chromosomes move to an equatorial plate
(metaphase plate)bull metaphase chromosomes can be stained and banded
Anaphasebull centromeres divide to create 2 chromosomes instead
of a pairbull the sister chromosomes are drawn to the opposite
poles of the cellbull exact division of chromosome 1 diploid complement
of genetic information to each daughter cell
Telophasebull nuclear envelopes reassemble and surround each set
of daughter chromosomes- chromosomes decondense
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5760
Mitosis in Action
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5860
Meiosis in
Action
In meiosis the process isquite similar to mitosisHowever another cell
division takes place in whichthere is no extra DNAreplication step Instead ofhaving a pair of genes (as ina diploid cell) there is onlyone copy of each gene (a
haploid cell) This one copyof genetic informationproduces gametes of eithersperm or eggs Thus onlyone copy of a gene is passedon to each gamete It is not
until the sperm and egg jointhat there will be two halvesof genetic information Thisprocess is the basis for all ofMendels laws
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 5960
frac12 to child frac12 to child
Looks like mom and dad
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
832019 Meiosis Krt
httpslidepdfcomreaderfullmeiosis-krt 6060
