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2
Types of Cell Types of Cell ReproductionReproduction
Asexual reproductionAsexual reproduction involves a involves a single cellsingle cell dividing to make dividing to make 2 2 new, identical daughter cellsnew, identical daughter cells
3 Reasons why cells undergo 3 Reasons why cells undergo asexual Reproduction:asexual Reproduction:
1.1. GrowthGrowth2.2. RepairRepair3.3. ReplacementReplacement
Examples: somatic cells (body), cancer Examples: somatic cells (body), cancer cellscells
3
Five Phases of the Cell Five Phases of the Cell CycleCycle
GG11 - primary growth phase - primary growth phaseS – synthesis; DNA replicatedS – synthesis; DNA replicatedGG22 - secondary growth phase - secondary growth phase
**collectively these 3 stages **collectively these 3 stages are called interphaseare called interphase
M - mitosisM - mitosisC - cytokinesisC - cytokinesis
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The Cell CycleThe Cell Cycle
DaughteDaughter Cellsr Cells
DNA DNA CopiedCopied
Cells Cells MaturMatur
ee
Cells prepare Cells prepare for Divisionfor Division
Cell Divides into Cell Divides into Identical cellsIdentical cells
http://www.cellsalive.com/mitosis.htm
Interphase
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• Occurs before Mitosis begins• Chromosomes are Chromosomes are copiedcopied (# doubles) (# doubles)• Chromosomes appear as threadlike coils Chromosomes appear as threadlike coils
((chromatinchromatin) at the start, but each ) at the start, but each chromosome and its copy (sister chromosome) chromosome and its copy (sister chromosome) change to change to sister chromatidssister chromatids at end of this at end of this phasephase
Remember:Remember:GG11 - primary growth phase - primary growth phaseS – synthesis; DNA replicatedS – synthesis; DNA replicatedGG22 - secondary growth phase - secondary growth phase
**collectively these 3 stages are **collectively these 3 stages are called called interphaseinterphase
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htmPhotographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Animal CellAnimal Cell Plant CellPlant Cell
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MitosisMitosisDivision of the Division of the
nucleusnucleusAlso called Also called
karyokinesiskaryokinesisOnly occurs in Only occurs in
eukaryotes eukaryotes (plants and (plants and animal cells)animal cells)
Has Has fourfour stages stagesDoesn’t occur in Doesn’t occur in
some cells such some cells such as as brain cellsbrain cells
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Four Mitotic StagesFour Mitotic Stages
ProProphasephaseMetaMetaphasephaseAnaAnaphasephaseTeloTelophasephase
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Early ProphaseEarly ProphaseChromatinChromatin in nucleus condenses to in nucleus condenses to
form form visible chromosomesvisible chromosomesMitotic spindle Mitotic spindle forms from fibers in forms from fibers in
cytoskeleton or cytoskeleton or centrioles (animal)centrioles (animal)
ChromosomesChromosomes
NucleolusNucleolus CytoplasmCytoplasm
Nuclear MembraneNuclear Membrane
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Late ProphaseLate ProphaseNuclear membrane & nucleolusNuclear membrane & nucleolus
are broken downare broken downChromosomesChromosomes continue continue
condensing & are condensing & are clearly visibleclearly visibleSpindle fibers called Spindle fibers called
kinetochoreskinetochores attach to the attach to the centromerecentromere of each chromosome of each chromosome
SpindleSpindle finishes forming finishes forming between the between the poles of the cellpoles of the cell
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Late ProphaseLate Prophase
Nucleus & Nucleolus have disintegratedNucleus & Nucleolus have disintegrated
ChromosomeChromosomes s
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Review of ProphaseReview of Prophase
What the cell What the cell looks likelooks like
What’s happeningWhat’s happening
12
MetaphaseMetaphaseChromosomes, attached to the Chromosomes, attached to the kinetochore kinetochore
fibersfibers, move to the center of the cell, move to the center of the cellChromosomes are now lined up at the Chromosomes are now lined up at the
equatorequatorMetaphase= Metaphase= “Middle”“Middle”
Pole of Pole of the Cellthe Cell
Equator of CellEquator of Cell
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MetaphaseMetaphase
ChromosoChromosomes lined mes lined at the at the EquatorEquator
The poles The poles of a cellof a cell
Spindle Spindle FibersFibers
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MetaphaseMetaphase
The pole of The pole of the cellthe cell
ChromosomesChromosomes at at EquatorEquator
Animal CellAnimal Cell
Plant CellPlant Cell
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Review of MetaphaseReview of Metaphase
What the cell What the cell looks likelooks like
What’s What’s occurringoccurring
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AnaphaseAnaphaseOccurs Occurs
rapidlyrapidlySister Sister
chromatidschromatids are pulled are pulled apart to apart to opposite opposite polespoles of the of the cell by cell by spindle spindle fibersfibers
Sister Sister Chromatids Chromatids
being being separatedseparated
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Anaphase ReviewAnaphase Review
What What the cell the cell looks looks likelike
What’s What’s occurrioccurri
ngng
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TelophaseTelophaseSister chromatids at Sister chromatids at opposite polesopposite polesSpindle Spindle disassemblesdisassemblesTwo new nuclei formTwo new nuclei formNuclear envelopeNuclear envelope forms around forms around
each set of sister chromatidseach set of sister chromatidsNucleolusNucleolus reappears reappearsCYTOKINESISCYTOKINESIS occurs occursChromosomes reappear as Chromosomes reappear as
chromatinchromatin
Telophase
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Animal Animal CellCell
Plant CellPlant Cell
Nuclei Nuclei reformingreforming
Polar Polar microtubules microtubules
continue continue elongationelongation
21
CytokinesisCytokinesisMeans division of the Means division of the
cytoplasmcytoplasmOccurs after mitosisOccurs after mitosisDivisionDivision of cell into two, of cell into two,
identical halves called identical halves called daughter daughter cellscells
In plant cells, cell plate In plant cells, cell plate forms forms at the equator to divide cellat the equator to divide cell
In animal cells, In animal cells, cleavage furrow cleavage furrow forms to split cellforms to split cell
22
CytokinesisCytokinesisCleavage Cleavage furrow in furrow in
animal cellanimal cell
Cell plate in Cell plate in plant cellplant cell
23
Daughter Cells of MitosisDaughter Cells of MitosisHave the Have the same number of same number of
chromosomes as each other chromosomes as each other and as the parent cell and as the parent cell from from which they were formedwhich they were formed
Identical Identical to each other, but to each other, but smaller than parent cellsmaller than parent cell
Must Must grow in sizegrow in size to become to become mature cells mature cells (G(G11 of Interphase) of Interphase)
24
Review Eukaryotic Cell Review Eukaryotic Cell DivisionDivision
Used for Used for growth and growth and repairrepair
Produce two new cells Produce two new cells identical to the original identical to the original cellcell
Cells are Cells are diploid (2n)diploid (2n)Chromosomes Chromosomes
during Metaphase during Metaphase of mitosisof mitosis
ProphaProphasese
MetaphaseMetaphase AnaphaseAnaphaseTelophaseTelophaseCytokinesisCytokinesis
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The Cell Cycle AnimationThe Cell Cycle AnimationYou should be able to name each You should be able to name each
stage!!stage!!
28
InterphaseInterphase
ProphaseProphase
MetaphaseMetaphaseAnaphaseAnaphase
TelophaseTelophase
Name the Mitotic Stages:Name the Mitotic Stages:
Name Name this?this?
Name this?Name this?
29
Mitosis in Onion Root Mitosis in Onion Root TipsTips
Do you see any stages of mitosis?Do you see any stages of mitosis?
35
Name the Stages of Name the Stages of Mitosis:Mitosis:
Interphase
Early prophase
Mid-ProphaseLate Prophase
Metaphase
Late Anaphase
Early Anaphase
Early Telophase
, Begin
cytokinesis
Late telophase, Advanced cytokinesis
36
Identify the StagesIdentify the Stages
Early, Middle, & Late Prophase Early, Middle, & Late Prophase
Late Late ProphaseProphase
MetaphaseMetaphase AnaphaseAnaphase
Late Late AnaphaseAnaphase
TelophaseTelophase Telophase & Telophase & CytokinesisCytokinesis
??
?? ?? ??
?? ?? ??
37
Locate the Four Mitotic Locate the Four Mitotic Stages in PlantsStages in Plants
MetaphasMetaphasee
ProphaseProphase
AnaphaAnaphasese
TelophaseTelophase
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Uncontrolled Mitosis If mitosis is not If mitosis is not
controlledcontrolled, , unlimited cell unlimited cell division occurs division occurs causing cancerous causing cancerous tumorstumors
OncogenesOncogenes are are special proteins special proteins that increase the chance increase the chance that a normal cell that a normal cell develops into adevelops into a tumor cell tumor cell
Cancer Cancer cellscells
40
Facts About MeiosisFacts About Meiosis
Preceded by interphase which Preceded by interphase which includesincludes chromosome chromosome replicationreplication
TwoTwo meiotic divisions --- meiotic divisions --- Meiosis I and Meiosis IIMeiosis I and Meiosis II
Called Reduction- divisionCalled Reduction- divisionOriginal cell is diploid (2n)Original cell is diploid (2n)Four daughter cellsFour daughter cells produced produced
that are that are monoploid (1n)monoploid (1n)
41
Facts About MeiosisFacts About MeiosisDaughter cellsDaughter cells contain half the contain half the
number of chromosomesnumber of chromosomes as the as the original celloriginal cell
ProducesProduces gametesgametes (eggs & (eggs & spermsperm))
Occurs in the Occurs in the testestestes in males in males ((SpermatogenesisSpermatogenesis))
Occurs in the Occurs in the ovariesovaries in in females (females (OogenesisOogenesis))
42
Start with Start with 46 double stranded 46 double stranded chromosomes (2n)chromosomes (2n)After 1 division - After 1 division - 23 double 23 double stranded chromosomes (n)stranded chromosomes (n)After 2nd division - After 2nd division - 23 single 23 single stranded chromosomes (n)stranded chromosomes (n) Occurs in our Occurs in our germ cellsgerm cells that that produce gametesproduce gametes
More Meiosis FactsMore Meiosis Facts
43
Why Do we Need Why Do we Need Meiosis?Meiosis?
It is the fundamental basis It is the fundamental basis of of sexual reproductionsexual reproduction
Two haploid (1n) gametes Two haploid (1n) gametes are brought together are brought together through through fertilizationfertilization to form to form a diploid a diploid (2n) zygote(2n) zygote
44
Fertilization – “Putting Fertilization – “Putting it all together”it all together”
1n =31n =3
2n = 62n = 6
45
Replication of Replication of ChromosomesChromosomes
ReplicationReplication is is the process of the process of duplicating a duplicating a chromosomechromosome
Occurs Occurs prior to prior to divisiondivision
Replicated Replicated copies are called copies are called sister sister chromatidschromatids
Held together at Held together at centromerecentromere
Occurs in Occurs in InterphasInterphas
ee
46
A Replicated A Replicated ChromosomeChromosome
HomologsHomologs (same genes, (same genes, different alleles)different alleles)
SisterSisterChromatidsChromatids(same genes,(same genes,same alleles)same alleles)
Gene XGene X
Homologs separate in meiosis I and Homologs separate in meiosis I and therefore different alleles separate.therefore different alleles separate.
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Meiosis Forms Haploid Meiosis Forms Haploid GametesGametes
Meiosis must Meiosis must reduce the chromosome number by halfreduce the chromosome number by half Fertilization then restoresFertilization then restores the 2n number the 2n number
from mom from dad child
meiosis reducesgenetic content
toomuch!
The right number!
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Meiosis: Two Part Cell Meiosis: Two Part Cell DivisionDivision
HomologsHomologsseparateseparate
Sister Sister chromatidschromatidsseparateseparate
DiploidDiploid
MeiosisMeiosis I I
MeiosisMeiosisIIII
DiploidDiploid
HaploiHaploidd
49
Meiosis I: Reduction DivisionMeiosis I: Reduction Division
NucleusNucleus SpindleSpindlefibersfibers NuclearNuclear
envelopeenvelopeEarly Early Prophase IProphase I(Chromoso(Chromosome number me number
doubleddoubled))
Late Late ProphasProphas
e Ie I
MetaphaMetaphase Ise I AnaphasAnaphas
e Ie ITelophase Telophase I I (diploid)(diploid)
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Prophase IProphase I
Early Early prophaseprophaseHomologs Homologs pair.pair.Crossing over Crossing over occursoccurs.
Late prophaseLate prophaseChromosomes Chromosomes condense.condense.Spindle forms.Spindle forms.Nuclear envelope Nuclear envelope fragments.fragments.
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Tetrads Form in Tetrads Form in Prophase IProphase I
Homologous Homologous chromosomeschromosomes
(each with sister chromatids) (each with sister chromatids)
Join to form aJoin to form a TETRADTETRAD
Called SynapsisCalled Synapsis
52
Crossing-OverCrossing-Over Homologous Homologous
chromosomeschromosomes in a tetrad in a tetrad cross over cross over each othereach other
Pieces of Pieces of chromosomes chromosomes or or genes are genes are exchangedexchanged
Produces Produces Genetic Genetic recombinationrecombination in the offspringin the offspring
54
Crossing-over multiplies the already Crossing-over multiplies the already huge number of different gamete huge number of different gamete types produced by independent types produced by independent
assortmentassortment
Crossing-OverCrossing-Over
55
Metaphase IMetaphase I
Homologous Homologous pairspairs of of
chromosomes chromosomes align along the align along the equatorequator of the of the
cellcell
56
Anaphase IAnaphase I
Homologs separateHomologs separate and move to opposite and move to opposite poles.poles.
Sister chromatids Sister chromatids remain remain attached attached at theirat their centromerescentromeres.
57
Telophase ITelophase I
Nuclear envelopes Nuclear envelopes reassemble.reassemble.
Spindle disappears.Spindle disappears.
Cytokinesis Cytokinesis divides cell divides cell into two.into two.
58
Meiosis IIMeiosis II
Only one homolog of Only one homolog of each chromosome is each chromosome is present in the cellpresent in the cell.
Meiosis II produces gametes Meiosis II produces gametes with with
one copy of each chromosome one copy of each chromosome and thus one copy of each and thus one copy of each gene.gene.
Sister chromatids carry Sister chromatids carry identical genetic identical genetic
informationinformation. .
Gene XGene X
59
Meiosis II: Reducing Meiosis II: Reducing Chromosome NumberChromosome Number
Prophase Prophase IIII
MetaphaMetaphase IIse II
AnaphasAnaphase IIe II
TelophasTelophase IIe II 4 Identical 4 Identical
haploid haploid cellscells
60
Prophase IIProphase II
Nuclear Nuclear envelope envelope fragments.fragments.
Spindle forms.Spindle forms.
61
Metaphase IIMetaphase II
Chromosomes align Chromosomes align along along equatorequator of cell of cell..
62
Anaphase IIAnaphase II
Sister Sister chromatidschromatids separate and separate and move to move to opposite polesopposite poles.
EquatorEquator
PolePole
63
Telophase IITelophase II
Nuclear envelope Nuclear envelope assembles.assembles.
Chromosomes Chromosomes decondense.decondense.
Spindle Spindle disappears.disappears.
Cytokinesis Cytokinesis divides cell into divides cell into two.two.
64
Results of MeiosisResults of MeiosisGametes (egg & Gametes (egg & sperm) formsperm) form
Four haploid cells Four haploid cells with one copy of each with one copy of each chromosome chromosome
One allele of each One allele of each genegene
Different Different combinations of combinations of alleles for different alleles for different genes along the genes along the chromosomechromosome
66
SpermatogenesisSpermatogenesisOccurs in the Occurs in the
testestestesTwo divisions Two divisions
produce 4 produce 4 spermatidsspermatids
Spermatids Spermatids mature into mature into spermsperm
Men produce Men produce about about 250,000,000 250,000,000 sperm per daysperm per day
69
OogenesisOogenesisOccurs in the Occurs in the ovariesovariesTwo divisions produce Two divisions produce 3 polar 3 polar
bodiesbodies that die and that die and 1 egg1 eggPolar bodies die because of Polar bodies die because of
unequal division of cytoplasmunequal division of cytoplasmImmature egg called Immature egg called oocyteoocyteStarting at puberty, one oocyte Starting at puberty, one oocyte
matures into an matures into an ovum (egg)ovum (egg) every 28 daysevery 28 days
71
OogenesisOogenesis
OogoniumOogonium(diploid)(diploid)
MitosisMitosis
PrimaryPrimaryoocyteoocyte(diploid)(diploid)
Meiosis IMeiosis I
SecondarySecondaryoocyteoocyte(haploid)(haploid)
Meiosis IIMeiosis II(if fertilization(if fertilizationoccurs)occurs)
First polar bodyFirst polar bodymay divide may divide (haploid)(haploid) PolarPolar
bodiesbodiesdiedie
Ovum (egg)Ovum (egg)
SecondSecondpolar bodypolar body(haploid)(haploid)
a
A
X
X
a
X
A X
a
X
a
X
MatureMatureeggegg
A
X
A
X
73
MitosisMitosis MeiosisMeiosisNumber of Number of
divisionsdivisions 1122
Number of Number of daughter cellsdaughter cells 22 44
Genetically Genetically identical?identical? YesYes NoNo
Chromosome #Chromosome # Same as Same as parentparent Half of parentHalf of parent
WhereWhere Somatic cellsSomatic cells Germ cellsGerm cells
WhenWhen Throughout Throughout lifelife
At sexual At sexual maturitymaturity
RoleRole Growth and Growth and repairrepair
Sexual Sexual reproductionreproduction
Comparison of DivisionsComparison of Divisions