1. Creating gametes (sex cells)
MEIOSIS
Creating gametes (sex cells)
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EQ: What is meiosis, and how is it different from mitosis?
EQ: Why is meiosis important for sexually reproducing organisms?

2. Gametes: Somatic Cells: Types of Cells Egg & sperm cells
Called haploid - contain 1 copy of every chromosome; “n”; 1/2 the amount of DNA for the organism
DNA can be passed to offspring
Somatic Cells:
ALL cells in your body except sex cells
Called diploid – contains 2 copies of every chromosome; “2n”; complete amount of DNA for the organism

3. B A Total number of chromosomes for the organism Somatic Cell n
Matching
Total number of chromosomes for the organism B A
Somatic Cell n
Dipl oid
Haplo id 2n
Half the number of chromosomes for the organism
Game te
liver cell
egg cell

4. Chromosomes Homologous chromosomes are similar, but not identical
Carry same genes in same order, but the form of the gene may not be the same
Ex: blue eye color gene vs brown eye color gene
Sister chromatids are identical copies of the same chromosome
A human body cell has 23 pairs of homologous chromosomes for a total of chromosomes.

5. What is Meiosis?
Meiosis is a two-part cell division process occurring in organisms who sexually reproduce that results in cells with half the number of chromosomes as a normal cell
The point of meiosis is to create gametes (egg & sperm cells) so that babies can be made
The random formation of gametes during meiosis creates genetic diversity in a population.

6. Mitosis vs. Meiosis Meiosis Mitosis Type of nuclear division
Results in 4 genetically different haploid cells
Involves sexual reproduction
2 divisions
Function: create sex cells
Mitosis
Type of nuclear division
Results in 2 genetically identical diploid cells
Involves asexual reproduction
1 division
Function: growth & repair

7. Mitosis vs. Meiosis

8. Phases of Meiosis: Meiosis 1
Occurs after DNA has been replicated
Divides homologus chromosomes in 4 phases (PMAT!)

9. Crossing Over
Occurs in Meiosis 1
a. Homologous chromosomes form a tetrad
b. Chromatids cross over one another
c. The crossed sections of chromatids are exchanged
***This produces a new combination of genes which contributes to diversity within a population. ***

10. Phases of Meiosis: Meiosis 2
NO DNA replication between meiosis 1 & meiosis 2
Divides sister chromatids in 4 phases (PMAT!)

11. Gametogenesis in males & females
Gametogenesis – production of gametes
Females: 1 diploid cell becomes 1 mature haploid cell
Males: 1 diploid cell becomes 4 mature haploid cells
This difference is because an egg cell contributes cytoplasm, organelles, and DNA to an embryo while a sperm contributes only DNA