1. START or Restriction Point The Cell Cycle

2. The Main Jobs of the Cell Cycle: 1.To accurately transmit the genetic information! 2.To maintain normal ploidy; i.e. diploidy! Euploidy: additions of whole chromosome sets e.g. n, 2n, 3n, 4n = haploid, diploid, triploid, tetraploid Aneuploidy: additions or subtractions of one or more single chromosomes e.g. 2n + 1, 2n -1, 2n + 2, etc.

3. Properties Required for Transmission of Chromosomes During Cell Division 1. One and only one centromere 2. Functional telomere at both ends 3. Chromosomes must be linear (i.e. fully replicated) 4. Chromosomes cannot be too large or too small

4. S Phase of the Cell Cycle

5. Mitosis

6. Fibroblasts in Culture blue = DNA green = microtubules

7. Mitosis in an Early Fruit Fly Embryo

8. Anaphase in a plant cell

9. Metaphase in a mammalian cell

11. G1-S and G2-M are the major control points in the cell cycle Rao and Johnson cell fusion experiments 1.Fuse M phase cell with interphase cell: Interphase nucleus enters M 2.Fuse S phase cell with G1 cell: The G1 nucleus enters S phase 3.Fuse S phase cell with G2 cell: The G2 nucleus does not enter S phase

12. Cyclin Dependent Kinase Regulate the Cell Cycle

13. Experimental Systems Important for Cell Cycle Studies Arbacia punctulata Xenopus laevisSchizosaccharomyces pombe Saccharomyces cerevisiae

14. Fission yeast: Schizosaccharomyces pombe

15. Budding Yeast Saccharomyces cerevisiae

16. Isolating Temperature Sensitive Mutants in Haploid Yeast

17. Permissive (low) temperatureRestrictive (high) temperature Cdc Mutants Arrest at the Same Cell Cycle Phase

18. cdc mutant growing at permissive temp (23C) cdc mutant growth arrested after 6 hrs at non-permissive temp (36C) The Behavior of a Temperature Sensitive cdc Mutant

19. How to Clone cdc Genes in Yeast

20. Cdc Genes Encode Proteins Needed for DNA Replication Studies in S. cerevisiae

21. Cdc Genes Encode Proteins Needed for the G2-M Transition: Studies in S. pombe cdc2 + encodes a kinase Moreover = cdc28 in S. cerevisiae!

22. Cyclin was Discovered in Sea Urchin Embryos Protein Level Time cyclin A cyclin B MMM can stimulate to lay lots of eggs

23. Frog life cycle 1 mm sperm tadpole feeds, grows and bcecomes an adult frog OOCYTE GROWS WITHOUT DIVIDING (MONTHS) FERTILIZATION FERTILIZED EGG DIVIDES WITHOUT GROWING (HOURS)

24. The Maturation of Frog Eggs

25. An Assay for Maturation Promoting Factor (MPF) Yoshio Masui, 1971

26. MPF Activity Peaks Before Each Cell Division Moreover, MPF has kinase activity

28. Purification of MPF: The Birth of Cyclin Dependent Kinases This is cdc2 + !! (Cdc28 in S. cerevisiae) This is cyclin!! Which = cdc13 + in S. pombe

29. Phosphorylation of CDK Targets Changes Their Activity Now performs a cell cycle function

30. The Nobel Prize in Physiology or Medicine, 2001 “ for their discovery of key regulators of the cell cycle ”