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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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Presentation Transcript


Context
Context:

  • Meiosis allows

    for the formation

    of sperm and

    egg cells


Overview
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
    Meiosis I: Interphase

    • The chromatin begins to condense into chromosomes, which duplicate

    • Identical to interphase in mitosis

    Chromosome duplication


    Meiosis i prophase i
    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
    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.


    Meiosis i metaphase i

    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


    Meiosis i anaphase 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


    Meiosis i telophase i and cytokinesis i

    The cell begins to divide into two daughter cells. of the cell.

    Each cell produced after cytokinesis has been reduce from diploid to haploid.

    Meiosis I: Telophase I (and cytokinesis I)


    Interphase
    Interphase: of the cell.

    Very short

    DNA is not replicated before meiosis II


    Meiosis ii prophase ii

    Nuclear membrane begins to dissolve of the cell.

    Spindle fibers begin to form

    Meiosis II: Prophase II


    Meiosis ii metaphase ii

    Spindle fibres attach to centromeres of the cell.

    Sister chromatids line up at equator

    Meiosis II: Metaphase II


    Meiosis ii anaphase ii

    Centromeres divide in two of the cell.

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

    Meiosis II: Anaphase II


    Meiosis ii telophase ii and cytokinesis ii

    Nuclear membrane reforms and cytoplasm divides of the cell.

    Meiosis II: Telophase II and (cytokinesis II)


    Result
    Result: of the cell.

    • Formation of four cells

      • Are sex cells (egg or sperm)

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


    Videos
    Videos: of the cell.

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

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


    To do
    To do: of the cell.

    • Meiosis colouring sheet

    • Read pages 103-107

      • Page 107 # 1, 2, 3, 4, 5, 6