1. Meiosis
Division of Sex Cells

2. Meiosis
A process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell.
Diploid – 2 sets of chromosomes
Haploid – 1 set of chromosomes
Homologous – chromosomes that each have a corresponding chromosome from the opposite sex parent

3. Meiosis

4. Meiosis Stages Meiosis usually involves 2 distinct stages Meiosis I
Meiosis II

5. Prophase I
Each chromosome pairs with its corresponding homologous chromosome to form a tetrad.
There are 4 chromosomes in a tetrad.
The pairing of homologous chromosomes is the key to understanding meiosis.
Crossing-over may occur here
Crossing-over is when chromosomes overlap and exchange portions of their chromatids.

6. Prophase I

7. Metaphase I
Spindle fibers attach to the chromosomes

8. Metaphase I

9. Anaphase I
The fibers pull the homologous chromosomes toward opposite ends of the cell.

10. Anaphase I

11. Telophase I & Cytokinesis
Nuclear membranes form.
The cell separates into 2 cells.

12. Telophase I

13. Cytokinesis

14. Prophase II Meiosis I results in two haploid (N) cells.
Each cell has half the number of chromosomes as the original cell.

15. Prophase II

16. Metaphase II
The chromosomes line up similar to metaphase in mitosis.

17. Metaphase II

18. Anaphase II
Sister chromatids separate and move to opposite ends of the cell.

19. Anaphase II

20. Telophase II
Meiosis II results in 4 haploid cells.

21. Telophase II

22. Gamete Formation In males, meiosis results in 4 sperm cells
In females, meiosis results in 1 egg cell and three polar bodies, which are not used in reproduction.

23. Mitosis vs Meiosis Mitosis Meiosis Results in 2 Diploid Cells (2N)
4 Haploid Cells (N)
Cells are
Genetically Identical
Genetically Different
Occurs in
Somatic (Body) Cells
Sex Cells