Cell Division and Mitosis

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