Meiosis

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  • Homologous means the same- in this case the same trait (may be different versions of this trait- brown eye gene vs. blue eyed gene)
  • Meiosis

    1. 1. Meiosis The beginning of Genetics
    2. 3. Meiosis vs. Mitosis <ul><li>Mitosis is used to make duplicate cells for growth, repair and replacement. </li></ul><ul><li>Meiosis is used to make sex cells </li></ul><ul><ul><li>For example: Eggs and Sperm </li></ul></ul><ul><li>Mitosis ends with the exact number of chromosomes as it began with </li></ul><ul><li>Meiosis reduces the number in half </li></ul><ul><ul><li>Meiosis is also referred to “reduction division” </li></ul></ul>
    3. 4. Interphase <ul><li>Cell starts out as a DIPLOID cell. Either a SPERMATOCYTE or an OOCYTE </li></ul><ul><li>Chromosomes replicate. </li></ul><ul><li>Chromosomes cannot be seen </li></ul>Nucleus Cell Membrane
    4. 5. Prophase I <ul><li>Nucleus starts to disappear. </li></ul><ul><li>Sister Chromatids pair up to form chromosomes, which now can be seen. </li></ul><ul><li>Homologous Chromosomes pair up to form tetrads. </li></ul><ul><li>Centrioles duplicate and move to the poles </li></ul>Centromere
    5. 6. What kind of cell is this? <ul><li>Haploid </li></ul><ul><li>Diploid </li></ul><ul><li>Homologous </li></ul><ul><li>None of the above </li></ul>1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
    6. 7. Metaphase I <ul><li>Spindle Fibers appear. </li></ul><ul><li>Tetrads line up along the middle of the spindle. </li></ul><ul><li>Fibers attach to centromere. </li></ul>Spindle Fibers
    7. 8. Anaphase I <ul><li>Spindle fibers pull the tetrads apart </li></ul><ul><li>Chromosomes are pulled to the centrioles. </li></ul>
    8. 9. Telophase I <ul><li>Spindle Fibers and centrioles disappear. </li></ul><ul><li>Nucleus reappears around each of the new sets of chromosomes. </li></ul><ul><li>Cell starts to form a break at the middle and starts to pinch in at the sides. </li></ul>
    9. 10. Telophase I (continued) <ul><li>Cell continues to split at the mid-line forming two cells. This cell splitting is called cytokinesis </li></ul>
    10. 11. Meiosis II Continues with both cells, but this will only show one
    11. 12. Prophase II <ul><li>Chromosomes are already visible </li></ul><ul><li>Nucleus disappears </li></ul><ul><li>Centrioles move to the poles </li></ul>
    12. 13. Metaphase II <ul><li>Spindle Fibers appear </li></ul><ul><li>Chromosomes are lined up along middle of cell </li></ul>
    13. 14. Anaphase II <ul><li>Chromosomes are pulled apart to the centrioles </li></ul>
    14. 15. Telephase II <ul><li>Spindle fibers and centrioles disappear </li></ul><ul><li>A nucleus appears around each set of chromosomes </li></ul><ul><li>Cell starts to pinch in at the center </li></ul>
    15. 16. Telephase II (Continued ) <ul><li>Both cells divide (cytokinesis), leaving 4 new cells </li></ul><ul><li>Each with half the number of chromosomes the original cell had. </li></ul><ul><li>Each cell is now HAPLOID, called a gamete. </li></ul><ul><li>Gametes can a be a sperm or an egg. </li></ul>
    16. 17. In what cells does meiosis occur? <ul><li>Skin </li></ul><ul><li>Hair </li></ul><ul><li>Reproductive organs </li></ul><ul><li>All of the above </li></ul>25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
    17. 18. Which of the following is a gamete? <ul><li>Sperm </li></ul><ul><li>Egg </li></ul><ul><li>Sex Cell </li></ul><ul><li>All of the above </li></ul>25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

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