[X-chromosome inactivation in mammalian ontogeny]

This review is dedicated to a very interesting problem of developmental genetics: dose compensation of the X-chromosome genes in somatic cells of female mammals. A sequence of events related to X-chromosome inactivation during cell differentiation at the early embryonic stages, association of distributed X-chromosome heterochromatization with developmental pathologies, evolutionary origin of X-inactivation, and its relationship with genomic imprinting are considered.