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  1. 1. Review of Mitosis Prophase Metaphase Anaphase Telophase 1 2 3 4
  2. 2. Overview of Mitosis: Prophase, Metaphase, Anaphase, Telophase
  3. 3. Overview of Meiosis: Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II, Telophase II
  4. 4. Prophase I <ul><li>In prophase I: </li></ul><ul><ul><li>The nuclear membrane breaks down </li></ul></ul>
  5. 5. Metaphase I <ul><li>In Metaphase I: </li></ul><ul><ul><ul><li>This is different than Metaphase in Mitosis </li></ul></ul></ul><ul><ul><ul><li>Chromosomes line up in pairs </li></ul></ul></ul><ul><ul><ul><li>Kinetochore fibers attach to centromeres </li></ul></ul></ul>
  6. 6. One thing that happens during metaphase I is that parts of the sister chromosomes can actually cross-over and switch. This allows for new combinations of genetic material. (This is why we don’t look just like our moms or dads) This is called genetic recombination.
  7. 7. Anaphase I <ul><li>In Anaphase I </li></ul><ul><ul><li>Homologous chromosomes seperate </li></ul></ul><ul><ul><ul><li>The chromatids do not seperate </li></ul></ul></ul>
  8. 8. Telophase I <ul><li>In Telophase I </li></ul><ul><ul><li>Cells Split </li></ul></ul><ul><ul><li>New Nuclear Membrane forms </li></ul></ul><ul><ul><ul><li>At this point, each cell has 46 chromosomes </li></ul></ul></ul><ul><ul><ul><li>2n </li></ul></ul></ul>
  9. 9. Prophase II <ul><li>In Prophase II: </li></ul><ul><ul><ul><li>These cells go straight from telophase I to prophase II. They skip interphase. </li></ul></ul></ul><ul><ul><ul><li>NO CELL CYCLE </li></ul></ul></ul>
  10. 10. Metaphase II <ul><li>In Metaphase II: </li></ul><ul><ul><li>Chromosomes line up along midline of cell </li></ul></ul>
  11. 11. Anaphase II <ul><li>In Anaphase II: </li></ul><ul><ul><li>CHROMATIDS separate </li></ul></ul><ul><ul><ul><li>Just like Mitosis </li></ul></ul></ul>
  12. 12. Telophase II <ul><li>In Telophase II: </li></ul><ul><ul><li>Nuclear Membrane begins to form </li></ul></ul><ul><ul><li>Each cell has 23 chromosomes </li></ul></ul><ul><ul><li>1n </li></ul></ul>
  13. 13. Review of the difference between Mitosis and Meiosis
  14. 14. Oogenesis <ul><li>Occurs in the ovaries </li></ul><ul><li>Two divisions produce 3 polar bodies that die and 1 egg </li></ul><ul><li>Polar bodies die because of unequal division of cytoplasm </li></ul><ul><li>Immature egg called oocyte </li></ul><ul><li>Starting at puberty, one oocyte matures into an ovum (egg) every 28 days </li></ul>
  15. 15. Spermatogenesis <ul><li>Occurs in the testes </li></ul><ul><li>Two divisions produce 4 spermatids </li></ul><ul><li>Spermatids mature into sperm </li></ul><ul><li>Men produce about 250,000,000 sperm per day </li></ul>
  16. 16. Questions <ul><li>What kind of cells are we creating during meiosis? </li></ul><ul><li>How many chromosomes do they end up with? </li></ul><ul><li>How many chromosomes do cells end with in mitosis? </li></ul>