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Mitosis: Cell Division

Explore the process of mitosis, cell division, and the cell cycle. Learn why cells divide and which cells divide often. Understand the phases of mitosis and the significance of cytokinesis. Discover how mitosis contributes to growth, repair, and the replacement of dead cells.

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Mitosis: Cell Division

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  1. Mitosis:Cell Division

  2. Why do cells divide? • Growth • Repair • Replace dead cells

  3. What cells divide often? • Skin • Stomach lining • Red Blood cells • Embryo • Plant roots • Hair • Nails

  4. What cells rarely/never divide? • Nervous System • Liver

  5. Why do we age? • Eventually cells stop being replaced • “Apoptosis” • Cell death • “We die because out cells die.” • William R. Clark

  6. “C” Terms • Chromosomes • Long threads of genetic material • Found in nucleus • Chromatid • One side of a duplicated chromosome

  7. “C” Terms • Centromere • Structures that hold sister chromatids together • NOTE • 2 sister chromatids = 1 duplicated chromosome

  8. “C” Terms • Chromatin • DNA tnagled around a histone (a protein) • Condensed chromatin = chromosome

  9. Huh? C. Duplicated chromosome A. DNA B. Chromatin histone

  10. “C” Terms • Centrioles • Small protein bodies • In cytoplasm • Animal cells only

  11. Cell Division in a Nutshell • Before: • Chromosome duplicates = 2 sister chromatids • During: • Sister chromatids separate • After: • 2 “daughter” cells • Genetically identical

  12. Cell Cycle • Mitotic phase • 10% • Interphase • 90%

  13. Interphase • Made up of three phases: • G1, S, G2 • What happens? • Things necessary to divide

  14. Interphase • G1 Phase • Cell Growth • 8-10 hours • S Phase • DNA replication • Chromosome replication • 6-8 hours • G2 Phase • More Cell Growth • Centriole replication • 4-6 hours

  15. Mitotic Phase • Mitosis • Division of nucleus (chromosomes) • Occurs after interphase • Cytokinesis • Division of cytoplasm • Creates 2 daughter cells • Occurs at the end of mitosis

  16. Mitosis Phases • Interphase • Prophase • Prometaphase • Metaphase • Anaphase • Telophase IPPMAT

  17. Task • Draw a diagram of mitosis • Label 6 phases & give each a short description IPPMAT

  18. Interphase • “Resting Phase” • Cell NOT dividing • Precedes mitosis • Prepares cell for division • How?

  19. Early Prophase • Centrioles: • Make spindle fibres • Move towards opposite plates • Chromosomes now visible

  20. Late Prophase • Centrioles reach poles • Nuclear membrane (envelope) & nucleolus start to disappear

  21. Metaphase • Spindle fibres attach to centromeres • Duplicate chromosomes line up at equator • Guided by spindle fibers

  22. Anaphase • Spindle fibers retract • Pull sister chromatids apart • Towards opposite polls

  23. Telophase • Chromatin reappears • Nuclear membrane & nucleolus reappear • Cytokinesis occurs • Result • Two daughter cells

  24. What phases do you see? B A C D

  25. Cytokinesis • Why would it occur differently in animal and plant cells? • Plant cells have a rigid cell wall!

  26. Cytokinesis Animal Cells Plant Cells • Cell membrane pinches inward • Creates cleavagefurrow • Think: • Pull a string around a balloon • Cell Plate forms between two new nuclei • Becomes cell wall

  27. Cytokinesis

  28. Cytokinesis

  29. Plant vs. Animal – Another Difference? • Centrioles not present in plant cells • What makes spindle fibers in plant cells? • Form from cytoskeleton

  30. Concept Map

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