a densely staining inactivated condensed X chromosome that is present in each somatic cell of most female mammals and is used as a test of genetic femaleness (as in a fetus) —called also sex chromatin
barr
noun(Barr body)
a herpesvirus (species Human herpesvirus 4 of the genus Lymphocryptovirus) that causes infectious mononucleosis and is associated with Burkitt's lymphoma and nasopharyngeal carcinoma —abbreviation EBV