BIO 2133 Chapter Notes - Chapter 5: Zygosity, Xist (Gene), Color Blindness
18 Sep 2016
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7. 5 dosage compensation prevents excessive expression of x-linked genes in mammals. Dosage compensation: a genetic mechanism that equalizes the levels of expression of genes at loci on the x chromosome. In mammals, this is accomplished by random inactivation of an x chromosome, leading to barr body formation. Barr bodies: murray l. barr & ewart j. bertram o. In drosophilia, the female does not deactivate an x chromosome but the x chromosome in the males produce twice as much: called a sex chromatin body or barr body. Barr body: an inactivated x chromosome that is densely staining dna positive mass seen in the somatic cells of mammalian females. Barr bodies follows the n-1 rule, where n is the total number of barr bodies. The lyon hypothesis: the proposal that there is random inactivation of the maternal or paternal. Individual cells were isolated following biopsy and cultured in vitro. A culture of cells derived from a single cell is called a clone.
