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Meiosis: The Process

Meiosis: The Process. Biology 12. Cartoon of the day:. Context: . Meiosis allows for the formation of sperm and egg cells. Overview:. Interphase Meiosis I Prophase I Metaphase I Anaphase I Telophase I (and cytokinesis) Meiosis II Prophase II Metaphase II Anaphase II

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Meiosis: The Process

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  1. Meiosis: The Process Biology 12

  2. Cartoon of the day:

  3. Context: • Meiosis allows for the formation of sperm and egg cells

  4. Overview: • Interphase • Meiosis I • Prophase I • Metaphase I • Anaphase I • Telophase I (and cytokinesis) • Meiosis II • Prophase II • Metaphase II • Anaphase II • Telophase II (and cytokinesis)

  5. Meiosis I: Interphase • The chromatin begins to condense into chromosomes, which duplicate • Identical to interphase in mitosis Chromosome duplication

  6. Meiosis I: Prophase I • In meiosis (unlike mitosis), the process called synapsis occurs. • Tetrads of homologous chromosome form • There may be an exchange of genetic material, called crossing over

  7. Crossing over (synapsis): • Non-sister chromatids of homologous chromosomes interchange genes • The pairing (formation of the tetrad) allows crossing over to take place and this enables genetic variations in the daughter cells.

  8. Tetrads line up at the equator Alignment is random so that chromosomes from one will be mixed with the other parent when they move apart Meiosis I: Metaphase I

  9. One homologous chromosome of each pair is pulled to each end of the cell. **Remember in mitosis, it was the chromatids that separated, not pairs of chromosomes! Meiosis I: Anaphase I

  10. The cell begins to divide into two daughter cells. Each cell produced after cytokinesis has been reduce from diploid to haploid. Meiosis I: Telophase I (and cytokinesis I)

  11. Interphase: Very short DNA is not replicated before meiosis II

  12. Nuclear membrane begins to dissolve Spindle fibers begin to form Meiosis II: Prophase II

  13. Spindle fibres attach to centromeres Sister chromatids line up at equator Meiosis II: Metaphase II

  14. Centromeres divide in two Spindle fibres pull sister chromatids towards opposite ends of cell (pole) Meiosis II: Anaphase II

  15. Nuclear membrane reforms and cytoplasm divides Meiosis II: Telophase II and (cytokinesis II)

  16. Result: • Formation of four cells • Are sex cells (egg or sperm) • Haploid (carries half the number of chromosomes of somatic cells)

  17. Videos: • http://www.youtube.com/watch?v=kVMb4Js99tA • http://www.youtube.com/watch?v=iCL6d0OwKt8

  18. To do: • Meiosis colouring sheet • Read pages 103-107 • Page 107 # 1, 2, 3, 4, 5, 6

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