1. Cell Division and Mitosis Chapter 10

2. 10.1 The Cycle of Cell Growth and Division: An Overview  The products of mitosis are genetic duplicates of the dividing cell  Chromosomes are the genetic units divided by mitosis

3. Mitotic Cell Division  DNA replication  Equal separation (segregation) of replicated DNA molecules  Delivery to daughter cells Two new cells, same information as parent cell

4. Mitosis  Mitosis is the basis for Growth and maintenance of body mass in multicelled eukaryotes Reproduction of many single-celled eukaryotes

5. Chromosomes  DNA of eukaryotic cells is divided among individual, linear chromosomes Located in cell nucleus  Ploidy of a cell or species Diploid (2n) Haploid (n)

6. Eukaryotic Chromosomes Fig. 10-2, p. 203

7. Sister Chromatids  DNA replication and duplication of chromosomal proteins produces two exact copies (sister chromatids)  Chromosome segregation occurs during cell division

8. 10.2 The Mitotic Cell Cycle  Interphase extends from the end of one mitosis to the beginning of the next mitosis  After interphase, mitosis proceeds in five stages  Cytokinesis completes cell division by dividing the cytoplasm between daughter cells

9. 10.2 (cont.)  The mitotic cell cycle is significant for both development and reproduction  Mitosis varies in detail, but always produces duplicate nuclei

10. Mitotic Cell Cycle  Includes mitosis and interphase  Mitosis occurs in five stages Prophase Prometaphase Metaphase Anaphase Telophase

11. The Cell Cycle Fig. 10-3, p. 203

12. Interphase Fig. 10-4a (1), p. 204

13. Fig. 10-4b, p. 205

14. Stage 1: Prophase  Chromosomes condense into short rods  Spindle forms in the cytoplasm

15. Prophase Fig. 10-4a (2), p. 204

16. Stage 2: Prometaphase  Nuclear envelope breaks down Spindle enters former nuclear area Sister chromatids of each chromosome connect to opposite spindle poles  Kinetochore of each chromatid attaches to the spindle microtubules

17. Prometaphase Fig. 10-4a, p. 204

18. Spindle Connections at Prometaphase Fig. 10-6, p. 206

19. Stage 3: Metaphase  Spindle is fully formed  Chromosomes align at metaphase plate Moved by spindle microtubules

20. Metaphase Fig. 10-4b, p. 204

21. Stage 4: Anaphase  Spindle separates sister chromatids and moves them to opposite spindle poles  Chromosome segregation is complete

22. Anaphase Fig. 10-4b, p. 204

23. Stage 5: Telophase  Chromosomes decondense Return to extended state typical of interphase  New nuclear envelope forms around chromosomes

24. Telophase Fig. 10-4b, p. 204

25. Animation: Mitosis step-by-step

26. Mitosis Fig. 10-5, p. 206

27. Cytokinesis  Division of cytoplasm completes cell division  Produces two daughter cells Each daughter nucleus produced by mitosis

28. Cytokinesis in Animal Cells  Proceeds by furrowing Band of microfilaments just under the plasma membrane contracts Gradually separates cytoplasm into two parts

29. Cytokinesis by Furrowing Fig. 10-8, p. 208

30. Plant Cytokinesis  Cell wall material is deposited along the plane of the former spindle midpoint  Deposition continues until a continuous new wall (cell plate) separates daughter cells

31. Cytokinesis by Cell Plate Formation Fig. 10-9, p. 208

32. 10.3 Formation and Action of the Mitotic Spindle  Animals and plants form spindles in different ways  Mitotic spindles move chromosomes by a combination of two mechanisms

33. Spindle Formation  In animal cells Centrosome divides, the two parts move apart Microtubules of the spindle form between them  In plant cells with no centrosome Spindle microtubules assemble around the nucleus

34. Centrosome and Spindle Formation Fig. 10-10, p. 210

35. In the Spindle  Kinetochore microtubules Run from poles to kinetochores of chromosomes  Nonkinetochore microtubules Run from poles to a zone of overlap at the spindle midpoint without connecting to chromosomes

36. A Fully Developed Spindle Fig. 10-11, p. 210

37. During Anaphase  Kinetochores move along kinetochore microtubules Pulling chromosomes to the poles  Nonkinetochore microtubules slide over each other Pushing the poles farther apart

38. Anaphase Spindle Movements Fig. 10-12, p. 211

39. Kinetochore Movement Fig. 10-13, p. 211

40. 10.4 Cell Cycle Regulation  Cyclins and cyclin-dependent kinases Internal controls that directly regulate cell division  Internal checkpoints Stop cell cycle if stages are incomplete  External controls Coordinate mitotic cell cycle of individual cells within overall activities of the organism

41. Cell Cycle Control (1)  Complexes of cyclin and a cyclin-dependent protein kinase (CDK) Directly control cell cycle  CDK Is activated when combined with a cyclin Adds phosphate groups to target proteins, activating them

42. Cell Cycle Control (2)  Activated proteins trigger the cell to progress to the next cell cycle stage  Each major stage of the cell cycle Begins with activation of one or more cyclin/CDK complexes Ends with deactivation of complexes by breakdown of cyclins

43. Cyclin/CDK Control Fig. 10-15, p. 214

44. Internal Controls  Important internal controls create checkpoints Ensure that the reactions of one stage are complete before cycle proceeds to next stage

45. External Controls  Based on surface receptors that recognize and bind signals Peptide hormones and growth factors Surface groups on other cells Molecules of the extracellular matrix  Binding triggers internal reactions that speed, slow, or stop cell division

46. Cancer  Control of cell division is lost Cells divide continuously and uncontrollably Form rapidly growing mass of cells that interferes with body functions  Cancer cells break loose from their original tumor (metastasize) Form additional tumors in other parts of the body

47. Tumor Cells Fig. 10-16, p. 215

48. Animation: Mitosis overview PLAY ANIMATION