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Meiosis

Meiosis. Overview of Meiosis. Cell goes through interphase and replicates the DNA during S Cell goes through meiosis I and cytokinesis The cell doesn’t go into interphase, but undergoes meiosis II and another cytokinesis

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Meiosis

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  1. Meiosis

  2. Overview of Meiosis • Cell goes through interphase and replicates the DNA during S • Cell goes through meiosis I and cytokinesis • The cell doesn’t go into interphase, but undergoes meiosis II and another cytokinesis • The result is 4 daughter cells that are haploid (one chromosome per pair)

  3. Prophase I • Chromatin condenses into chromosomes • Nuclear membrane breaks down • Spindles form • Homologs synapse and cross over

  4. KARYOTYPE SHOWING HOMOLOGOUS CHROMOSOMES

  5. Prophase I Continued • In crossing over, chromatids of homologs cross over, break off, and reattach to its homolog • http://www.phschool.com/science/biology_place/biocoach/meiosis/proi.html

  6. Metaphase I • Chromosomes move to the middle of the cell (metaphase plate or equator) with their homologs

  7. Anaphase I • Homologs separate and move to the poles (sister chromatids do NOT separate)

  8. Telophase I & Cytokinesis • Nuclear membranes reform around each set of DNA • Overlaps with cytokinesis • The cell then divides through cytokinesis • The cell does NOT grow and begins meiosis II

  9. http://www.phschool.com/science/biology_place/biocoach/meiosis/mei1ani.htmlhttp://www.phschool.com/science/biology_place/biocoach/meiosis/mei1ani.html

  10. Prophase II • Nuclear envelope breaks down • Chromatin condenses into chromosomes • Spindle is formed and attaches to chromatids • http://www.phschool.com/science/biology_place/biocoach/meiosis/proii.html

  11. Metaphase II • Chromosomes line up on the equator (metaphase plate)

  12. Anaphase II • Chromatids separate and move towards opposite ends of the cell (poles) • http://www.phschool.com/science/biology_place/biocoach/meiosis/anaii.html

  13. Telophase II & Cytokinesis • Nuclear membranes reform around the DNA • Chromosomes reform chromatin • Spindle breaks down • Cell then divides • http://www.phschool.com/science/biology_place/biocoach/meiosis/mei2ani.html

  14. RESULTS • 4 haploid daughter cells • Daughter cells are genetically different due to crossing over • In animals, this makes gametes (reproductive cells) • It is important gametes be haploid so a diploid chromosome number is achieved at fertilization

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