1. How does meiosis form the gametes?

2. Meiosis is 2 Cell Divisions
1st Cell Division
2nd Cell Division
4 Haploid Cells
1 Diploid cell

3. Prior to Cell Division
Prior to cell division (mitosis or meiosis) the cell’s chromosomes must replicate.

4. Stages of Meiosis Meiosis I - two cells
Meiosis II – four cells with ½ the chromosome number
Each meiotic cell division has the same stages (prophase, metaphase, anaphase, Telophase, cytokinesis)

5. Meiosis I

6. Crossing over – Prophase I
Synapsis – homologous chromosomes pair up
Crossing over – chromosomes overlap and exchange of genes.

7. Meiosis II

8. Movie

9. Summary How are mitosis and meiosis different?
What type of cells are produced by meiosis?
What happens before cell division?
How many cells are produced by meiotic cell division?
Are they diploid or haploid?
What is synapsis?
What is crossing over?

10. Production of gametes (sperm & egg) By meiotic cell division
Gametogenesis
Gameto = gametes
Genesis = creation
Production of gametes (sperm & egg)
By meiotic cell division

11. Creation of an ovum or egg cell by meiotic cell division in the ovary.
Oogenesis
Creation of an ovum or egg cell by meiotic cell division in the ovary.

12. How many eggs are produced?
There is an unequal sharing of cytoplasm
1 egg & 3 non functional polar bodies

13. Egg vs. Polar Bodies
The egg is very large, has most of the cytoplasm, which will provide nutrients for the offspring.

14. Creation of sperm cells by meiotic cell division in the testes.
Spermatogenesis
Creation of sperm cells by meiotic cell division in the testes.

15. How many sperm are produced by spermatogenesis?
4 equal sized sperms with flagella for swimming.

16. Spermatogenesis vs. Oogenesis

17. What is essential for sexual reproduction?
Gametes must have:
motility to be able to meet and unite
food to nourish the developing embryo

18. What is the difference?
Sex cells Vs
Body cells

19. What type of cell division produces body cells?
Mitosis = My toes

20. What type of cell division produces sex cells?
Meiosis x

21. Which of the two cell divisions leads to variation?
Meiosis = VARIATION
Mitosis = CLONES

22. Summary What is gametogenesis? Where does gametogenesis happen?
What type of cells are produced by gametogenesis?
What are the two types of gametogenesis?
How many eggs are produced?
How many sperms are produced?

23. Mitosis vs. Meiosis Points of Comparison Mitosis Meiosis
# of cell divisions
Exchange of genetic material between chromosomes
# of functioning cells produced from the original
Genetic makeup of final cells produced
Function of cells produced in multicellular organisms