1. Mitosis & meiosis Gametogenesis & fertilization References: Alberts, et al. 2008. Molecular Biology of the Cell, 5 th ed., Garland Science, NY. Hickman, et al. 2006. Integrated Principles of Zoology, 13 th ed., McGraw-Hill, NY. Hoefnagels, Mariëlle. 2009. Biology, 1 st ed., McGraw-Hill, NY; Ch 8-9. Mader, Sylvia S. 2010. Biology, 10 th ed., McGraw-Hill, NY; Ch 9-10.

2. The cell cycle G1G1 S G2G2 M

4. Cell cycle ●Interphase –G 1, S, G 2 ●Mitosis –Cytokinesis is division of 1 cell into 2. –Mitosis is separation of chromatids. ●In preparation for cytokinesis ●Chromatids are replicate chromosomes. G1G1 S G2G2 M

5. Figure 4-1 Molecular Biology of the Cell (© Garland Science 2008)‏

6. Mitosis & cytokinesis

7. Phases of mitosis ●Prophase –Chromatin condenses into chromosomes. ●Metaphase –Chromosomes line up across cell. ●Anaphase –Spindle fibers pull chromatids apart. ●Telophase –Chromosomes separate into daughter cells.

8. Ploidy doesn't change during mitosis. ●Ploidy: # of homologues –Homologues: versions of same chromosome –Don't confuse with chromatids ●Haploid (n) or diploid (2n) ●Parent cell is 2n daughter cells are 2n ●Parent cell is n daughter cells are n

9. Mitosis Metaphase 2n

10. Meiosis I Metaphase I Meiosis II Metaphase II 2n n n n n n n n

11. Meiosis ●Segregation of homologous chromosomes ●Into haploid gametes ●Meiosis I is the reduction division ●Meiosis II works like mitosis –(But the cells are already haploid)

12. Meiosis I (reduction division) ●Prophase I –Chromatin condenses into chromosomes. ●Metaphase I –Homologous pairs line up across cell. ●Anaphase I –Spindle fibers pull homologues apart. ●Telophase I –Chromosomes separate into daughter cells. ●Ploidy is reduced from 2n to n

13. Meiosis II ●Metaphase II –Chromosomes line up across cell. ●Anaphase II –Spindle fibers pull chromatids apart. ●Telophase II –Chromosomes separate into daughter cells. ●Parent and daughter cells are haploid.

14. Gametogenesis ●Spermatogenesis in mammals ●Oogenesis in mammals

15. Spermatogenesis in mammals ●Primary spermatocyte (2n) ●Secondary spermatocytes (n) ●Spermatids (n) ●Sperm (n)

16. Oogenesis in mammals ●Primary oocyte (2n) ●Secondary oocyte and polar bodies (1n)

17. Fertilization ●Ovum (1n) and sperm (1n) combine ●Zygote (2n) results

18. Fertilization and activation Prevention of polyspermy  Fast block Change in membrane potential.  Slow block Cortical reaction causes vitelline membrane to separate from cell membrane.

19. Figure 08.04 From Hickman et al. 2006 (13th ed.)‏