Bio Cell Division


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Bio Cell Division

  1. 1. Cell Division
  2. 2. Chromosomes <ul><li>Are made of DNA </li></ul><ul><li>Each chromosome consists of sister chromatids attached at a centromere </li></ul>
  3. 3. Cell Cycle <ul><li>During the cell cycle, a cell grows, prepares for division, and divides to form 2 daughter cells, each of which then begins the cycle again. </li></ul><ul><li>Interphase – time for growth and regular cell activity. </li></ul><ul><li>Most of a cell’s life is spent in Interphase. </li></ul>
  4. 4. Interphase
  5. 5. Introduction to Cell Division A time when a cell performs its usual functions, depending on the location in the body.
  6. 6. Mitosis <ul><li>The division of somatic or regular cells. </li></ul><ul><li>Its divided into 4 phases. </li></ul><ul><li>Remember Interphase is NOT part of Mitosis. </li></ul>
  7. 7. Introduction to Mitosis
  8. 8. Prophase <ul><li>First stage of Mitosis </li></ul><ul><li>Chromatin condenses into chromosomes </li></ul><ul><li>Centrioles separate and a spindle fiber begins to form. </li></ul><ul><li>Nuclear membrane breaks down </li></ul>
  9. 9. Prophase
  10. 10. Metaphase <ul><li>Second Phase of Mitosis </li></ul><ul><li>Chromosomes line up in the middle of the cell. </li></ul><ul><li>Each chromosome is connected to a spindle fiber. </li></ul>
  11. 11. Metaphase
  12. 12. Anaphase <ul><li>Third Phase of Mitosis </li></ul><ul><li>The sister chromatids separate into individual chromosomes and move apart to opposite ends of the cell. </li></ul>
  13. 13. Anaphase
  14. 14. Telophase <ul><li>Fourth and Final Stage of Mitosis </li></ul><ul><li>Chromosomes gather at opposite ends of the cell and lose their distinct shapes </li></ul><ul><li>Two new nuclear membranes have formed. </li></ul>
  15. 15. Telophase
  16. 16. Cytokinesis <ul><li>The cytoplasm pinches in half. </li></ul><ul><li>Each daughter cell has an identical set of duplicate chromosomes </li></ul>
  17. 17. Regulating the Cycle <ul><li>A protein called cyclin helps regulate the cell cycle in eukaryotic cells. </li></ul><ul><li>They respond to internal and external events. These proteins are regulators. </li></ul>
  18. 18. When Things Go Wrong <ul><li>Cancer cells do not respond to the signals that regulate the growth of most cells. </li></ul><ul><li>As a result, they form masses of cells called tumors that can damage surrounding tissues. </li></ul>
  19. 19. The Cell Cycle in Depth <ul><li>Interphase </li></ul><ul><li>Mitotic Stage </li></ul><ul><li>Cytokinesis </li></ul><ul><li>Apoptosis </li></ul><ul><li>Cell Cycle and Cancer </li></ul>
  20. 20. INTERPHASE <ul><li>3 STAGES </li></ul><ul><ul><li>G 1 stage </li></ul></ul><ul><ul><li>S Stage </li></ul></ul><ul><ul><li>G 2 Stage </li></ul></ul><ul><ul><li>Some cells such as nerve and muscle cells typically do NOT complete the cell cycle and are said to have entered the G 0 stage. </li></ul></ul><ul><ul><li>For adult mammalian cells, interphase lasts ~20 hours (90% of cell cycle) </li></ul></ul>
  21. 21. INTERPHASE: G 1 stage <ul><li>Stage BEFORE DNA replication </li></ul><ul><li>Cell doubles its organelles and accumulates materials for DNA synthesis </li></ul><ul><li>G used to stand for “gap” but now it stands for “growth” </li></ul><ul><ul><li>Protein synthesis is a part of these growth stages </li></ul></ul>
  22. 22. INTERPHASE: S stage <ul><li>DNA synthesis/replication occurs </li></ul><ul><ul><li>Each chromosome is composed of one chromatid (DNA double helix) and makes 2 sister chromatids (2 identical DNA double helix molecules) </li></ul></ul>
  23. 23. INTERPHASE: G 2 stage <ul><li>Stage from the completion of DNA replication to the onset of mitosis </li></ul><ul><ul><li>The cell synthesizes protein that will assist cell division (i.e. protein found in microtubules) </li></ul></ul>
  24. 24. M (Mitotic Stage) <ul><li>The cell division stage that includes mitosis (nuclear division) and cytokinesis (division of the cytoplasm) </li></ul>
  25. 25. Prophase <ul><li>Nucleolus is disappearing </li></ul><ul><li>Nuclear envelope is fragmenting </li></ul><ul><li>Spindle is forming between centrosomes </li></ul><ul><li>Asters radiate from the centrioles within the centrosomes </li></ul>
  26. 26. Prometaphase <ul><li>Kinetochores of sister chromatids attach to kinetochore spindle fibers extending from opposite poles </li></ul><ul><li>Chromosomes move back and forth until they are aligned at the metaphase plate </li></ul>
  27. 27. Metaphase <ul><li>Spindle is fully formed </li></ul><ul><li>Duplicated chromosomes align at metaphase plate </li></ul><ul><li>Spindle consists of polar spindle fibers that overlap at the metaphase plate </li></ul><ul><li>Kinetochore spindle fibers that are attached to chromosomes </li></ul>
  28. 28. Anaphase <ul><li>Sister chromatids separate to become daughter chromosomes that move toward the poles </li></ul><ul><li>Polar spindle fibers slide past one another </li></ul><ul><li>Kinetochore spindle fibers disassemble </li></ul><ul><li>Cytokinesis by furrowing begins </li></ul>
  29. 29. Telophase <ul><li>Nuclear envelopes re-form </li></ul><ul><li>Chromosomes begin changing back to chromatin </li></ul><ul><li>Nucleoli reappear </li></ul><ul><li>Spindle disappears </li></ul>
  30. 30. Plant Cells <ul><li>Lack centrioles and asters </li></ul><ul><li>Mitotic spindle still forms and goes through the same 5 mitotic phases </li></ul>
  31. 31. Cytokinesis <ul><li>In animal cells, it’s a furrowing process that divides the cytoplasm </li></ul><ul><li>In plant cells, the formation of a cell plate from which the plasma membrane and cell wall are completed </li></ul>
  32. 32. The Cell Cycle and Cancer <ul><li>Cancer is due to the mutation of genes that control the cell cycle </li></ul><ul><li>Cancer cells are… </li></ul><ul><ul><li>Are Nondifferentiated </li></ul></ul><ul><ul><li>Divide repeatedly </li></ul></ul><ul><ul><li>Have abnormal nuclei </li></ul></ul><ul><ul><li>Don’t require growth factors </li></ul></ul><ul><ul><li>Not constrained by their neighbors </li></ul></ul>
  33. 33. The Cell Cycle and Cancer <ul><li>After forming a tumor, cancer cells metastasize and start new tumors elsewhere in body. </li></ul><ul><li>What you can do to try to prevent cancer… </li></ul><ul><ul><li>Avoid unnecessary radiation </li></ul></ul><ul><ul><li>Avoid exposure to organic chemicals (ex: tobacco smoke) </li></ul></ul><ul><ul><li>Have a diet rich in fruits and vegetables </li></ul></ul>
  34. 34. Prokaryotic Cell Division <ul><li>Prokaryotic chromosome has a few proteins and a single, long loop of DNA </li></ul><ul><li>Binary fission- the chromosome attaches to the inside of the plasma membrane and replicates. </li></ul><ul><li>As cell elongates, the chromosomes are pulled apart </li></ul><ul><li>Inward growth of the plasma membrane and formation of new cell wall material divide the cell in 2. </li></ul>
  35. 35. Prokaryotic vs. Eukaryotic Cells <ul><li>Binary fission (in prokaryotes) and mitosis (in cellular eukaryotic protists and fungi) allow organisms to reproduce asexually </li></ul><ul><li>Mitosis in multicellular eukaryotes is primarily for the purpose of development, growth, and repair of tissues. </li></ul>