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).
Word origin: named after its discoverer Murray Llewellyn Barr, a Canadian anatomist who first identified the particle in the nucleus of neurons of female cats.
Synonym: sex chromatin
See also: Barr test