<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-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.</n0:def-definition><n0:def-source>NCI</n0:def-source></n0:ComplexDefinition>