Barr body is heterochromatic X chromosome occurring in female placental mammals. It was first found by Barr and Bertram (1949) in nerve cells of female cats & later in cells of human females by Barr in (1960). Number of Barr body is one less than the total number of X chromosomes. Basically it is absent in male but if one barr body is present in males then it lead to Klinefelter’s syndrome.