1. Meiosis
Creation of sex cells

2. Diploid vs Haploid Diploid Haploid 2 copies of each chromosome
All our body cells are diploid 2n
Haploid
one copy of each chromosome
Our sex cells (sperm, egg) are haploid 1n
*n= number of copies of chromosome*

3. Why Meiosis? Humans are ___________: 23 pairs of chromosomes
Sex cells are ___________: contain 1 set of 23 chromosomes
Fertilization of two _____________ (sperm and egg) create one ZYGOTE that is __________
Sexual reproduction creates a zygote that is genetically different than both its parents

4. Why Meiosis? Humans are DIPLOID: 23 pairs of chromosomes
Sex cells are HAPLOID: contain 1 set of 23 chromosomes
Fertilization of two SEX CELLS (sperm and egg) create one ZYGOTE that is DIPLOID
Sexual reproduction creates a zygote that is genetically different than both its parents

5. First division
Second division

6. Stages
The stages look very similar to the stages of mitosis- a few differences:
Meiosis I
Homologous chromosomes pair (tetrad) and line up at equator
Sister chromatids move to the SAME pole of the cell
“Tetrad”

7. Stages
Meiosis II
Each daughter cell continues to divide to produce two haploid cells
No replication of DNA between Meiosis I and Meiosis II

8. Increasing Genetic Diversity
During Meiosis I two steps are key in increasing genetic diversity
Crossing over: During Prophase I
Homologous chromosomes exchange pieces of DNA
2. Independent assortment: During Anaphase II
Homologous chromosomes and/or sister chromatids are randomly assigned to each daughter cell

9. Crossing Over

10. Independent Assortment

11. Video
Meiosis

12. Stages of Meiosis
Cut out the stages and paste them in the correct order
Label Meiosis I and Meiosis II
Label each stage
Colour each chromosome and track it through the stages
Indicate where crossing over occurs
Indicate where independent assortment occurs