1. 2 Meiosis and Gametogenesis Chapter 1 Thompson and Thompson

2. Somatic and Germline cells Development of a fertilized egg into an adult results in two distinct types of cells –Somatic cells These create all tissues and organs of the adult except for cells destined to become sperm or egg They can only undergo mitosis –Germline cells The final differentiated form of these cells are mature gametes: the sperm and egg These cells undergo mitosis until gametogenesis –They then undergo meiosis

3. Meiosis

4. Meiosis is required for gametogenesis

5. Meiosis I Somatic cells Germline Cells

6. Interphase I and Prophase I Leptotene

7. Prophase I Zygotene

8. Prophase I Pachytene

9. Prophase I Diplotene

10. Recombination

11. And on the molecular level

12. Metaphase I and anaphase I

13. Meiosis I is the reduction division

14. Non-disjunction

15. Telophase I

16. Cytokinesis sperm formationoocyte formation

17. Meiosis II

18. A comparison of meiosis and mitosis MitosisMeiosis Chromosome number MaintainsReduces Nuclear Divisions12 Cells resulting24 Cells involvedSomaticGermline

19. And now, Meiotic “Titanic”

20. Relationship to Gametogenesis

21. Sperm and Egg formation

22. Gametogenesis

23. Fertilization Entry of a single sperm into an egg prevents entry of other sperm The DNA of sperm and egg are initially kept separate in “pronuclei” of the zygote Timing of a pregnancy extends from the “last menstrual period” (LMP) rather than the time of fertilization

24. Mitotic Non-disjunction