Mitosis meiosis Gametogenesis fertilization References Alberts et al

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. , Mc. Graw-Hill, NY. Hoefnagels, Mariëlle. 2009. Biology, 1 st ed. , Mc. Graw-Hill, NY; Ch 8 -9. Mader, Sylvia S. 2010. Biology, 10 th ed. , Mc. Graw-Hill, NY; Ch 9 -10.

The cell cycle G 2 M G 1 S

The cell cycle

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

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

Mitosis & cytokinesis

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.

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

Mitosis 2 n 2 n 2 n Metaphase

2 n Meiosis I n n Metaphase I n Meiosis II n n Metaphase II

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)

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 2 n to n

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.

Gametogenesis ● Spermatogenesis in mammals ● Oogenesis in mammals

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

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

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

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

Figure 08. 04 From Hickman et al. 2006 (13 th ed. )