X chromosome inactivation, also called the Lyon hypothesis, is a phenomenon that occurs in every female mammal that has the double X chromosome configuration. Based on her own work on mice with mottled coats, Mary F. Lyon of the Medical Research...

X-inactivation (also called lyonization) is a process by which one of the two copies of the X chromosome present in female mammals is inactivated. The inactive X chromosome is silenced by packaging in repressive heterochromatin. X-inactivation occurs so...