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Xx if all genes were expressed on both x chromosomes

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Unformatted text preview: if all genes were expressed on both X chromosomes, we would have a gene dosage of 2 → detrimental (results in double the amount of proteins) 10 Aneuploidy X-inactivation -expression of X-linked genes on all but one X chromosome is repressed (some genes near telomere and centromere of short arm escape repression) -results in no increase in protein levels for most X-linked genes in cells 11 X inactivation -occurs in many mammalian species -16 d gestation (~800 cells) -one X chromosome is randomly inactivated -exists as a highly condensed body within the cell referred to as a Barr body (Dr. Barr was Canadian) XX XY 12 13 X inactivation -tendency to clonally keep the same X off -females; 50/50 expression mix of father’s X genes and mother’s X genes = genetic mosaic 14 Why are calicos almost always female? Females: XBXb Males: XbY (black) or XbY (orange co-dominant, except on the X allele, so males can’t have it. xxy...
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