geneticsppt_aneuploidy

geneticsppt_aneuploidy - Significant results of meiosis: 1....

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Significant results of meiosis: 1. Haploid cells are produced because two rounds of division follow one round of chromosome replication. 2. Alignment of paternally and maternally inherited chromosomes is random in metaphase I, resulting in random combinations of chromosomes in each gamete. Number of possible chromosome arrangements = 2 n -1 . Number of gametes with different genotypes = 2 n . 3. Crossing-over between maternal and paternal chromatids during meiosis I provides still more variation. Moreover, the crossing-over sites vary from one meiosis to another.
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The number of possible combinations of maternal and paternal homologues is 2 n , where n = the haploid number of chromosomes. In this diagram, the haploid number is 3, and 8 (2 3 ) different combinations are produced.
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Spermatogenesis in animals • Spermatogonial cells divide by mitosis, producing two cells – one becoming the primary spermatocyte • primary spermatocyte undergoes meiosis producing four spermatids that mature into sperm cells
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oogenesis • Specialized cells in the ovary (oogonia), begin Prophase I producing primary oocytes • Primary oocytes are arrested until sexual maturity, then they are periodically activated to go through the remaining stages of development • the primary oocyte goes through MI, producing one large secondary oocyte and one small polar body • upon ovulation the secondary oocyte undergoes MII which will be completed upon fertilization
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Plants – alternation of generations • Life cycles of plants alternate between a haploid gametophyte and a diploid sporophyte • Sporophytes undergo meiosis – anthers &
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geneticsppt_aneuploidy - Significant results of meiosis: 1....

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