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3 16 Crossing Over

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3 16 Crossing Over

  1. 1. Launch <ul><li>Write the definition of a gene and an allele. </li></ul><ul><li>What are the 8 stages of meiosis? </li></ul>
  2. 2. Cell Division <ul><li>In cell division, new cells are made from an old cell. </li></ul><ul><li>During cell division, these chromosomes are copied and one set of chromosomes are given to each new cell. </li></ul>
  3. 3. Meiosis <ul><li>8 stages: </li></ul><ul><li>Prophase I </li></ul><ul><li>Metaphase I </li></ul><ul><li>Anaphase I </li></ul><ul><li>Telophase I </li></ul><ul><li>Prophase II </li></ul><ul><li>Metaphase II </li></ul><ul><li>Anaphase II </li></ul><ul><li>Telophase II </li></ul>
  4. 4. Homologous Chromosomes <ul><li>Homologous Chromosomes are chromosomes that contain the same genes, but not necessarily the same alleles </li></ul>B b A A c c d D
  5. 5. Crossing Over <ul><li>Crossing over is a process in which different parts of homologous chromosomes switch places </li></ul><ul><li>Crossing over leads to increased genetic recombination </li></ul><ul><li>This occurs during Prophase I </li></ul>
  6. 7. II. Cell Division-Meiosis -Crossing over and the exchange of genes in meiosis is a major source of variation among organisms. In meiosis, you end up with 4 daughter cells that can be combined with another sex cell to make a new organism. MEIOSIS I MEIOSIS II Possible gametes Possible gametes Chromosome A Chromosome B Chromosome a Chromosome b
  7. 8. <ul><li>http://www.youtube.com/watch?v=pdJUvagZjYA&feature=related </li></ul>

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