1. Chapter 12 The Cell Cycle

3. Cell division requires coordinated division of chromosomes (mitosis) ….. …… and division of the cytoplasm (cytokinesis).

5. LE 12-2 Reproduction 100 µm Tissue renewal Growth and development 20 µm 200 µm

9. LE 12-3 25 µm 1888 W. Waldeyer was the first to introduce the term chromosome meaning “ colored body”.

13. Cell Cycle next

16. Video: Animal Mitosis Video: Sea Urchin (time lapse) Animation: Mitosis (All Phases ) Animation: Mitosis Overview Animation: Late Interphase Animation: Prophase Animation: Prometaphase Animation: Metaphase Animation: Anaphase Animation: Telophase Mitotic Animations and Videos

19. LE 12-7 Microtubules Chromosomes Sister chromatids Aster Centrosome Metaphase plate Kineto- chores Kinetochore microtubules 0.5 µm Overlapping nonkinetochore microtubules 1 µm Centrosome The Mitotic Spindle: A Closer Look

21. Chromosome movement Microtubule Motor protein Chromosome Kinetochore Tubulin subunits What is happening at the kinetochore? The kinetochore motor proteins detach and reattach to the kinetochore microtubule, this causes the microtubule to shorten (depolymerize) and thus moving the chromosome.

24. LE 12-9a Cleavage furrow 100 µm Contractile ring of microfilaments Daughter cells Cleavage of an animal cell (SEM)

25. LE 12-9b 1 µm Daughter cells Cell plate formation in a plant cell (TEM) New cell wall Cell plate Wall of parent cell Vesicles forming cell plate

26. LE 12-10 Nucleus Cell plate Chromosomes Nucleolus Chromatin condensing 10 µm Prophase. The chromatin is condensing. The nucleolus is beginning to disappear. Although not yet visible in the micrograph, the mitotic spindle is starting to form. Prometaphase. We now see discrete chromosomes; each consists of two identical sister chromatids. Later in prometaphase, the nuclear envelope will fragment. Metaphase. The spindle is complete, and the chromosomes, attached to microtubules at their kinetochores, are all at the metaphase plate. Anaphase. The chromatids of each chromosome have separated, and the daughter chromosomes are moving to the ends of the cell as their kinetochore micro- tubules shorten. Telophase. Daughter nuclei are forming. Meanwhile, cytokinesis has started: The cell plate, which will divide the cytoplasm in two, is growing toward the perimeter of the parent cell.

28. Origin of replication Cell wall Plasma membrane Bacterial chromosome E. coli cell Two copies of origin Chromosome replication begins. Soon thereafter, one copy of the origin moves rapidly toward the other end of the cell. Binary Fission

29. LE 12-11_2 Origin of replication Cell wall Plasma membrane Bacterial chromosome E. coli cell Two copies of origin Chromosome replication begins. Soon thereafter, one copy of the origin moves rapidly toward the other end of the cell. Replication continues. One copy of the origin is now at each end of the cell. Origin Origin

30. LE 12-11_3 Origin of replication Cell wall Plasma membrane Bacterial chromosome E. coli cell Two copies of origin Chromosome replication begins. Soon thereafter, one copy of the origin moves rapidly toward the other end of the cell. Replication continues. One copy of the origin is now at each end of the cell. Origin Origin Replication finishes. The plasma membrane grows inward, and new cell wall is deposited. Two daughter cells result.

32. LE 12-12 Bacterial chromosome Chromosomes Microtubules Prokaryotes Dinoflagellates Intact nuclear envelope Kinetochore microtubules Kinetochore microtubules Intact nuclear envelope Diatoms and yeasts Centrosome Most eukaryotes Fragments of nuclear envelope

35. The Rao Johnson Experiment Experiment 1 Experiment 2 S S S G 1 G 1 M M M When a cell in the M phase was fused with a cell in G 1 , the G 1 cell immediately began mitosis—a spindle formed and chromatin condensed, even though the chromosome had not been duplicated. Something in M phase induced interphase cells to divide. When a cell in the S phase was fused with a cell in G 1 , the G 1 cell immediately entered the S phase—DNA was synthesized. S cells contained something that induced regulation in G 1 cells.

42. LE 12-15 G 1 G 1 checkpoint G 1 G 0 If a cell receives a go-ahead signal at the G 1 checkpoint, the cell continues on in the cell cycle. If a cell does not receive a go-ahead signal at the G 1 checkpoint, the cell exits the cell cycle and goes into G 0 , a nondividing state.

44. LE 12-17 Petri plate Scalpels Without PDGF With PDGF Without PDGF With PDGF 10 mm

46. LE 12-18a Cells anchor to dish surface and divide (anchorage dependence). When cells have formed a complete single layer, they stop dividing (density-dependent inhibition). If some cells are scraped away, the remaining cells divide to fill the gap and then stop (density-dependent inhibition). 25 µm Normal mammalian cells

48. LE 12-18b Cancer cells do not exhibit anchorage dependence or density-dependent inhibition. Cancer cells 25 µm

51. Cancer cell Blood vessel Lymph vessel Tumor Glandular tissue Metastatic tumor A tumor grows from a single cancer cell. Cancer cells invade neighboring tissue. Cancer cells spread through lymph and blood vessels to other parts of the body. A small percentage of cancer cells may survive and establish a new tumor in another part of the body. Cancer

52. Chapter 12 The Cell Cycle THE END!