a mechanism that equalizes the expression of genes on the X chromosomes of males and females. In mammals, one X chromosome is deactivated to form a Barr body. Dominant--- that allele which will be phenotypically expressed when present.
The phenomenon in women, who have two copies of genes on the X chromosome, of having the same level of the products of those genes as males (who have a single X chromosome). This is due to the process of inactivation of one of the X chromosomes in females (Lyonization). See Lyon's hypothesis.
The process in organisms using a chromosomal sex determination mechanism (such as XX versus XY) that allows standard structural genes on the sex chromosome to be expressed at the same levels in females and males, regardless of the number of sex chromosomes. In mammals, dosage compensation operates by maintaining only a single active X chromosome in each cell; in Drosophila, it operates by hyperactivating the male X chromosome.
Any mechanism that balances gene expression between the sexes during critical early stages of development.
The imbalance caused by having two copies of the X chromosome in females compared to only one copy in males is countered (in humans) by X inactivation or (in Drosophila) by reducing the relative level of activity of X linked genes in females.
Dosage compensation is a genetic regulatory mechanism which operates to equalize the phenotypic expression of characteristics determined by genes on the X chromosome so that they are equally expressed in the human XY male and the XX female. Dosage compensation also occurs in other organisms like the fruit fly Drosophila melanogaster and the round worm Caenorhabditis elegans.