barr body definition
Barr body. The small, dark-staining mass of inactive X chromosome within the nucleus of non-dividing cell. Barr bodies are previously used as the basis for sex determination especially during the Olympics (see Barr test).
A Barr body (named after discoverer Murray Barr) is the inactive X chromosome in a female somatic cell, rendered inactive in a process called lyonization, in those species in which sex is determined by the presence of the Y (including humans) or W chromosome rather than the diploidy of the X.