Meiosis the process
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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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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

    • Telophase II (and cytokinesis)


  • Meiosis I: Interphase

    • The chromatin begins to condense into chromosomes, which duplicate

    • Identical to interphase in mitosis

    Chromosome duplication


    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


    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.


    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


    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


    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)


    Interphase:

    Very short

    DNA is not replicated before meiosis II


    Nuclear membrane begins to dissolve

    Spindle fibers begin to form

    Meiosis II: Prophase II


    Spindle fibres attach to centromeres

    Sister chromatids line up at equator

    Meiosis II: Metaphase II


    Centromeres divide in two

    Spindle fibres pull sister chromatids towards opposite ends of cell (pole)

    Meiosis II: Anaphase II


    Nuclear membrane reforms and cytoplasm divides

    Meiosis II: Telophase II and (cytokinesis II)


    Result:

    • Formation of four cells

      • Are sex cells (egg or sperm)

      • Haploid (carries half the number of chromosomes of somatic cells)


    Videos:

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

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


    To do:

    • Meiosis colouring sheet

    • Read pages 103-107

      • Page 107 # 1, 2, 3, 4, 5, 6


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