Final answer:
In female mammals, X inactivation randomly condenses one X chromosome in each cell into a Barr body, serving as dosage compensation to balance gene expression relative to males.
Step-by-step explanation:
The phenomenon of X inactivation is a biological process by which female mammals equalize the dosage of X chromosome genes relative to males. During early embryonic development, one of the two X chromosomes in each female cell becomes tightly condensed into a structure known as a Barr body. The decision as to whether the maternally or paternally derived X chromosome will be inactivated is random, and once X inactivation has occurred, it is passed on to all descendant cells. Notably, some genes on the inactivated X chromosome may remain active, and for the maturation of female ovaries, the inactive X chromosomes may need to reactivate. X inactivation serves as a mechanism of dosage compensation to ensure that females, which have two X chromosomes, do not overexpress X-linked genes compared to males, who have only one X chromosome. This process can be visually observed in tortoiseshell cats where different coat color patterns reflect the inactivation of different X chromosomes in different areas of the body during embryonic development.