BCOR 101

Sept 2, 2004

Mitosis and the Cell Cycle

•Genetic information is copied exactly in daughter cell

•Cell cycle is regulated by cyclins and CDKs

•Molecular motors at the kinetechore help separate chromosomes

Fig. 1.14 Eukaryotic cell cycle

Fig. 1.15 Interphase and mitosis in an animal cell

Understand the steps in mitosis and be able to draw the chromosomes in various stages

Meiosis

•Produces reduced (haploid) gametes by independent assortment of chromosomes

•Homologs pair, so there can be crossing over and recombination

Fig. 1.20 The stages of meiosis in an animal cell

Understand the steps in meiosis and be able to draw the chromosomes in various stages.

Consequences of meiosis

•Produces haploid gametes by independent assortment

•Convince yourself that independent assortment happens only in meiosis and not in mitosis.

•Crossing over breaks up sets of genes which

–Creates more genetic variation

–Allows loss of deleterious mutations

we talked a bit about how, without recombination, deleterious mutations would enexorably accumulate on chromosomes. That is probably one of the reasons that few lineages are completely asexual. With recombination, it is possible to generate new chromosome combinations that contain fewer mutations and thus have higher fitness. Convince yourself that this is true.

Fig. 1.22 Comparison of mitosis and meiosis in a diploid cell

This figure should be familiar to you

Test yourself:

•An animal cell has 8 chromosomes at G1. How many chromosomes and how many molecules of DNA does the cell have at:

•Metaphase of mitosis?

•Metaphase 1 of meiosis?

•Metaphase 2 of meiosis?

Chapter 1 problems

•In general, you should try to do all of the problems at the end of the chapters.

•Here are some particularly useful ones from chapter 1:

–1.3, 1.5, 1.9, 1.10, 1.12, 1.13, 1.14, 1.15, 1.19