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Chromosomes, Mitosis and Meiosis

Chromosomes, Mitosis and Meiosis. Chapter 10. Learning Objective 1. What is the significance of chromosomes in terms of information?. Chromosomes. Organization. Genes cell’s informational units made of DNA Chromatin DNA and protein makes up chromosomes (eukaryotes) Chromosomes

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Chromosomes, Mitosis and Meiosis

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  1. Chromosomes, Mitosis and Meiosis Chapter 10

  2. Learning Objective 1 • What is the significance of chromosomes in terms of information?

  3. Chromosomes

  4. Organization • Genes • cell’s informational units • made of DNA • Chromatin • DNA and protein • makes up chromosomes (eukaryotes) • Chromosomes • allow DNA sorting • into daughter cells

  5. KEY CONCEPTS • In eukaryotic cells, DNA is wound around specific proteins to form chromatin, which in turn is folded and packaged to make individual chromosomes

  6. Learning Objective2 • How is DNA organized in prokaryotic and eukaryotic cells?

  7. Prokaryotic Cells • Contain circular DNA molecules

  8. Eukaryotic Chromosomes • Nucleosome • histone (protein) bead wrapped in DNA • organized into coiled loops • held together by nonhistone scaffolding proteins

  9. Nucleosomes

  10. DNA wound around a cluster of histone molecules Histone tails Linker DNA Nucleosome (10 nm diameter) Fig. 10-2a, p. 213

  11. 100 nm Fig. 10-2b, p. 213

  12. Scaffolding Proteins

  13. DNA Scaffolding proteins 2 μm Fig. 10-3, p. 213

  14. Chromosome Organization

  15. 1400 nm 300 nm fiber (looped domains) 700 nm 30 nm chromatin fiber DNA wound around a cluster of histone molecules Scaffolding protein Condensed chromosome Condensed chromatin Extended chromatin Packed nucleosomes Histone 10 nm Nucleosomes 2 nm DNA double helix Fig. 10-4, p. 214

  16. Learning Objective3 • What are the stages in the eukaryotic cell cycle, and their principal events?

  17. Eukaryotic Cell Cycle • Cycle of cell division • interphase • M phase

  18. INTERPHASE G1 (First gap phase) S (Synthesis phase) G2 (Second gap phase) M PHASE (Mitosis and cytokinesis) Fig. 10-5, p. 215

  19. Interphase • First gap phase (G1 phase) • cell grows and prepares for S phase • Synthesis phase (S phase) • DNA and chromosome protein synthesis • chromosome duplication • Second gap phase (G2 phase) • protein synthesis increases • preparation for cell division

  20. M Phase • Mitosis • nuclear division • two nuclei identical to parent nucleus • Cytokinesis • cytoplasm divides • two daughter cells

  21. KEY CONCEPTS • Cell division is an important part of the cell cycle, which consists of the successive stages through which a cell passes

  22. Animation: The Cell Cycle CLICKTO PLAY

  23. Learning Objective4 • What is the structure of a duplicated chromosome, including the sister chromatids, centromeres, and kinetochores?

  24. A Duplicated Chromosome • Consists of a pair of sister chromatids • containing identical DNA sequences • Centromere • constricted region • joins sister chromatids • Kinetochore • protein to which microtubules bind • attached to centromere

  25. Sister Chromatids

  26. Centromere region Microtubules Kinetochore Sister chromatids 1.0 μm Fig. 10-7, p. 218

  27. Learning Objective5 • What is the process and significance of mitosis?

  28. Mitosis • Preserves chromosome number • in eukaryotic cell division • Identical chromosomes are distributed to each pole of the cell • nuclear envelope forms around each set

  29. Interphase

  30. INTERPHASE PROPHASE PROMETAPHASE Sister chromatids of duplicated chromosome Nucleolus Kinetochore Chromatin Nucleus Pieces of nuclear envelope Spindle microtubule Nuclear envelope Centrioles Developing mitotic spindle Plasma membrane Fig. 10-6a, p. 216

  31. Prophase • Chromatin condenses into duplicated chromosomes (pair of sister chromatids) • Nuclear envelope begins to disappear • Mitotic spindle begins to form

  32. Mitotic Spindle

  33. Metaphase plate (cell’s midplane) Kinetochore microtubule (spindle microtubule) Centrioles Astral microtubules Pericentriolar material Polar (non- kinetochore) microtubule Sister chromatids Fig. 10-9a, p. 219

  34. 10 μm Fig. 10-9b, p. 219

  35. Prophase

  36. Prometaphase • Spindle microtubules attach to kinetochores of chromosomes • Chromosomes begin to move toward cell’s midplane

  37. Prometaphase

  38. Metaphase • Chromosomes align on cell’s midplane (metaphase plate) • Mitotic spindle is complete • Microtubules attach kinetochores of sister chromatids to opposite poles of cell

  39. Metaphase

  40. Anaphase • Sister chromatids separate • move to opposite poles • Each former chromatid is now a chromosome

  41. Anaphase

  42. Telophase • Nuclear envelope re-forms • Nucleoli appear • Chromosomes uncoil • Spindle disappears • Cytokinesis begins

  43. Telophase

  44. METAPHASE ANAPHASE TELOPHASE 25 μm Spindle Cleavage furrow Centriole pair at spindle pole Reforming nuclear envelope Daughter chromosomes Cell’s midplane (metaphase plate) Fig. 10-6b, p. 217

  45. KEY CONCEPTS • In cell division by mitosis, duplicated chromosomes separate (split apart) and are evenly distributed into two daughter nuclei

  46. Cytokinesis

  47. Cleavage furrow Actomyosin contractile ring 10 μm Fig. 10-10a, p. 220

  48. Small vesicles fuse, forming larger vesicles Cell plate forming Nucleus Vesicles gather on cell’s midplane New cell walls (from vesicle contents) Eventually one large vesicle exists Plasma membrane Cell wall Cell plate forming New plasma membranes (from vesicle membranes) 5 μm Fig. 10-10b, p. 220

  49. Learning Objective6 • How is the cell cycle controlled?

  50. Cell-Cycle Control • Cyclin-dependent kinases (Cdks) • protein kinases that control cell cycle • active only when bound to cyclins • Cyclins • regulatory proteins • levels fluctuate during cell cycle

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