Dosage compensation:
A mechanism by which species with sex chromosomes ensure that the homogametic sex does not have too much or the heterogametic sex too little activity of loci on the homogametic sex chromosome. The process, in organisms using a chromosomal sex determination mechanism (such as XX versus XY), that allows standard structural genes on the homogametic sex chromosome to be expressed at the same levels in females and males, regardless of the number of homogametic sex chromosomes. In mammals, dosage compensation operates by maintaining only a single active X chromosome in each cell (see Lyon hypothesis), while in Drosophila it operates by hyperactivating the single male X chromosome.
|
