6.1 Sexual Reproduction and MeiosisAsexual Reproduction vs Sexual Reproduction

Requires ____________________ Requires two parentsProduces offspring__________ to the parent. Produces offspring _________ from the parents.Can produce_________ offspring very ______ Requires _________ time and ____________to

produce offspringResults in limited ____________within a species Results in lots of ________________ within a speciesMitosis is one form of asexual reproduction and results in offspring that are _____________ to parent

Meiosis is used to produce specialized sex cells called __________________: ___________(from males) and ___________ (from females), which combine to produce a new individual.

How SEX Works: Two Parents Genetic Diversity

Process of Fertilization:

1. single sperm penetrates the outer covering of the ______________ (egg)

2. Nuclei of sperm and ovum fuse = single __________________cell is formed

The fertilized cell is called a ____________________. The zygote begins to divide by _________________ producing more cells. Once a zygote becomes two cells, it is called an _________________. The embryo increases in size by further cell division (mitosis) and eventually develops specialized cells which make up various body structures in an organism.

Embryo: Forms from the Zygote due to __________

Zygote:____________________

DNA in Body Cells and Mitosis

Chromosomes are DNA! Chromosomes contain genetic information Mitosis ensures all cells in the body (except sex cells)

have the same DNA and the same number and kind of chromosomes

Mitosis occurs in somatic or ______________ cellsEx:

Mitosis (Review) – Division of one cell that results in

___________ genetically identical daughter cells

Cells must divide for __________, to replace dead cells, _________ of tissues, and asexual reproduction

Diploid Cells

Every organism has its own unique number of chromosomes. Humans have _______________.

This is called its diploid number or the total number of chromosomes in a somatic cell.

Diploid means “2 ________” and is written as “2N”.

Body cells of adult organisms have 2 sets of (matching) chromosomes – called _______________________chromosomes

1 set from female parent and 1 set from male parent

2 new ___________ cells identical to

parent cell

Chromosomes duplicated

during interphase________ cell

Cell division

Meiosis –Cell division to create sex cells for sexual reproduction– a process in which the number of chromosomes in the original cell is reduced by ___________ through the

separation of homologous chromosomes.

Meiosis occurs in sex organs only1. Males (XY) – sex organs are the ______________ in males2. Females (XX) – sex organs are the _____________ in females3. Meiosis also occurs in the sex organs of other animals, plants, fungi, etc…

Two Parts: Meiosis I- PMAT I and Meiosis II-PMAT II

VIEW MEIOSIS ANIMATION(S)

Refer to text p. 198-199 for detailed diagrams of all stages of meiosis

Division 1 Division 2

Daughter cells (gametes) have ______ as many chromosomes as parent cell

Haploid Cells Meiosis produces _________________– sex cells with ½ the number of chromosomes as the original cell

1. Males – meiosis produces ____sperm cells

2. Females – meiosis produces 1 (viable) egg The other 3 cells are called polar bodies – they give up their __________________ to nourish the 1 good egg.

3. Egg and sperm (sex cells) are also called gametes

4. Gametes have ½ the number of chromosomes as somatic (body) cells. We call this the _____________ number. Haploid means “1 set” and is written as “N”.

The human diploid number is 46, so its haploid number is ______

Diploid # of a fly – 8 Haploid # of a fly – ______ When does meiosis occur in humans?

1. Males beginning at puberty2. Females before birth – all eggs are produced before birth and at puberty eggs mature

Chromosome Number Each organism is unique. It has the same kind and number of chromosomes in somatic cells. To keep the number the same the chromosome number in sex cells must be _________ during meiosis

Ex: Humans have 46 chromosomes in their somatic cells, but23 chromosomes in their sex cells (_________ and ___________)

Without meiosis …………

Fertilized egg – zygote

Zygote develops into embryo and finally adult organism

by_______________46

23

23

Fertilized egg – zygote

92

46

46

Chromosome number not maintaineda non-viable

organism is produced

Meiosis involves the pairing of homologous chromosomes:

Homologous (matching) chromosomes pair up before 1st cell divisionHomologous chromosomes:

-look alike-genes code for same ___________________ -receive one from each parent

During 1st division, homologous chromosomes exchange genes during process called “____________________________”

These homologous chromosomes split up during meiosis – so chromosomes in gametes are different from each other due to crossing over

Crossing over increases ___________________ variation and is one reason why siblings look different

Independent Assortment: Occurs in meiosis I during Anaphase I when the homologous pairs are separated and randomly placed in different cells to greater genetic diversity in daughter cells.

View INDEPENDENT ASSORTMENT ANIMATION / Meiosis and Genetics 2 – Diversity- www.biomanbio.com

To Do! 1. Complete Mitosis Vs Meiosis comparison sheet refer to class notes for both!2. Snurfle Lab and handout3. For marks: Phases of Meiosis in class assignment

No crossing over – daughter cells are

identical to parent cells

Crossing over occurs –causes genetic variation(Daughter cells ar`e NOT identical to parent cell)

Comparing Mitosis and Meiosis

Meiosis MitosisWhere does this process occur?

Male (XY) = in_____________

Female (XX) = in____________ in __________________________

What kind of cells are produced?When does this

occur?Male (XY) = puberty

Female (XX) = _________________Any time

# of Divisions(Draw picture)

____ ____

# of Daughter cells produced

Male (XY) = _____ sperm

Female (XX) = ____ viable egg(s)_____

# of Chromosomes in daughter cells

________ as many as parent cellhaploid or N

In humans ___chromosomes/gamete

Same as parent celldiploid or 2N

In humans _____chromosomes/cell

Type of Reproduction

Genetic Composition

Daughter cells areidentical / not identical

to parent cellGenetic variation

Daughter cells areidentical / not identical

to parent cell

Pairing of Homologous Chromosomes

YES / NOCrossing over of genes occurs during

________phase ___ of meiosisYES / NO

Function/Importance To produce haploid cells called: ___________________

Growth, repair; development of adult from zygote