Editing X-inactivation (section)

===== Inheritance of inactivation status across cell generations =====

The descendants of each cell which inactivated a particular X chromosome will also inactivate that same chromosome. This phenomenon, which can be observed in the coloration of [[tortoiseshell cat]]s when females are [[heterozygous]] for the [[sex linkage|X-linked]] pigment gene, should not be confused with [[mosaic (genetics)|mosaicism]], which is a term that specifically refers to differences in the [[genotype]] of various cell populations in the same individual; X-inactivation, which is an [[epigenetics|epigenetic]] change that results in a different phenotype, is ''not'' a change at the [[genotype|genotypic]] level. For an individual cell or lineage the inactivation is therefore [[Skewed X-inactivation|skewed]] or '[[Skewed X-inactivation|non-random]]', and this can give rise to mild symptoms in female 'carriers' of [[X-linked]] genetic disorders.<ref>{{cite journal | vauthors = Puck JM, Willard HF | title = X inactivation in females with X-linked disease | journal = The New England Journal of Medicine | volume = 338 | issue = 5 | pages = 325–8 | date = January 1998 | pmid = 9445416 | doi = 10.1056/NEJM199801293380611 }}</ref>