BIOL239 Lecture Notes - Lecture 12: Xyy Syndrome, Monosomy, Gamete
18 Sep 2018
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Document Summary
Changes in chromosome number chapter 9 pages 325-335 (9. 4-9. 5) pages 192-193 (6. 3) Results from the loss or gain of one or more chromosomes. Aneuploids individuals whose chromosome number is not an exact multiple of the haploid number (n) for the species. Monosomic (most common: lacking 1 chromosome from the diploid number (2n-1, generally lethal in humans (autosomes) Tetrasomic: having 4 copies of a particular chromosome (2n+2) Autosomal aneuploidy is generally deleterious to the organism. Meiosis problem: option a, meiosis i homologs do not separate properly (2n to 2n & 0n instead of. 2n to 1n & 1n); nondisjunction happens: meiosis ii happens normally but the nondisjunction in meiosis i leads to. Reality is that trisomy 21 males are always infertile. Must have at least one x for viability gene dosage: gene dosage is the number of copies of a gene present in a cell, need dosage of one for most genes on x chromosome.
