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Meiosis
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Meiosis involves 2 parents (usually)
hereditary material is exchanged (mixed and transferred) Each species has a specific number of chromosomes For example humans total number of chromosomes is 46 diploid number is 46 or 2n = 46 the number of chromosomes in the gametes is the haploid number or n = 23 Other examples: crayfish 2n = 126 fruit flies 2n = 4
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Meiosis Meiosis animation (1:49 min):
Beginning of third class
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Vocabulary Diploid Haploid Germ cell (Gamete) Somatic cell Interphase
Prophase Metaphase Anaphase Telophase Cytokinesis
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Each resulting cell still has chromosomes from mom & dad
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Interphase Meiosis is preceded by interphase
chromosomes have not yet condensed
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Interphase chromosomes have replicated, and the chromatin begins to condense
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Meiosis Prophase I the chromatin shortens to form chromosomes
homologous chromosomes pair up or synapse to form tetrads
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Synapsis in Prophase I of Meiosis
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Meiosis Metaphase I chromosomes line up across the middle, or equator, of the cell centromeres of chromosomes attach to spindle fibres
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Meiosis Anaphase I homologous chromosomes separate and move along spindle fibres towards the poles or ends of the cell
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Meiosis Telophase I & Cytokinesis
cell begins to divide into two daughter cells each daughter cell can get any combination of maternal and paternal chromosomes cell has divided into two daughter cells
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Meiosis Prophase II nuclear membrane dissolves and the spindle fibres begin to form
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Meiosis Metaphase II as in Meiosis I, the chromosomes line up on the spindle fibers sister chromatids remain attached at their centromeres
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Meiosis Anaphase II centromeres split and sister chromatids separate and move to opposite poles of the cell chromatids are now called chromosomes
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Telophase II & Cytokinesis
With the formation of four cells, meiosis is over. Each of these prospective germ cells carries half the number of chromosomes of somatic cells.
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Comparing Mitosis and Meiosis
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Comparing Chromosome Numbers in Mitosis and Meiosis
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