X inactivation

<cell biology> The inactivation of one or other of each pair of X chromosomes to form the Barr body in female mammalian somatic cells.

Thus tissues whose original zygote carried heterozygous X borne genes should have individual cells expressing one or other but not both of the X borne gene products. The inactivation is thought to occur early in development and leads to mosaicism of expression of such genes in the body.

See: Lyon hypothesis.

(18 Nov 1997)


Terms mentioned in text: cell biology, inactivation, pair, x chromosomes, barr body, female, somatic cells, thus, tissues, original, zygote, heterozygous, genes, individual, cells, gene products, inactivation, early, development, leads, mosaicism, expression, genes, body, lyon hypothesis
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