X-Chromosome Inactivation

**Semantic type:** Genetic Function

**Definition:** A human early embryonic event in which in any given cell one of a female's two X chromosomes becomes inactivated and converted into a Barr body. After inactivation has occurred, all descendants of that cell have the same inactivated X chromosome. Thus, X-inactivation creates cell clones with differing effective gene content. An organism whose cells vary in effective gene content and hence in the expression of a trait, is called a genetic mosaic.

**Synonyms:** - Lyonization - X Chromosome Inactivation - X Inactivation - X-Inactivation