sex-related%20inh

sex-related%20inh - SEX-RELATED INHERITANCE Barr bodies;...

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SEX-RELATED INHERITANCE Barr bodies; the Lyon Hypothesis and dosage compensation In 1949, Murray Barr found that staining cat cells with Feulgen, a stain that binds to DNA, often resulted in the appearance of a "drumstick" in interphase nuclei, but only if the cat was female. Later it was learned that cells of normal human females also have a " Barr body " and that Triplo X females have 2 Barr bodies, per cell, Turner's none etc. Mary Lyon correctly hypothesized that the Barr Bodies are actually condensed, inactive X chromosomes : She also said that: • Every X > 1 is condensed and inactive in gene expression; • X-inactivation occurs early in development; • When it occurs, which X is inactivated in any cell is chance; • The same X remains inactive in all daughter cells in subsequent cell divisions. The Lyon Hypothesis explains: Dosage compensation , that is, why normal males and females have the same amount of gene products or enzymes coded for by sex- linked genes; For example, X Cf /X females have the same amount of
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sex-related%20inh - SEX-RELATED INHERITANCE Barr bodies;...

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