X-Chromosome Inactivation

X-Chromosome Inactivation is a biological process that occurs in female mammals, including humans. Females have two X chromosomes, while males have one X and one Y chromosome. To balance gene expression between the sexes, one of the two X chromosomes in each female cell is randomly turned off or "inactivated." This ensures that females, like males, effectively use the genes carried on a single X chromosome. The inactivation is permanent in that cell and its descendants, leading to a mosaic pattern of gene expression across tissues. This process plays a significant role in genetic diversity and certain diseases.