Explanation

Sex Chromatin in Interphase Nuclei Barr and Bertram (1949) found that interphase nuclei of human females stained with orcein possess small distinct chromatin body called sex chromatin, Barr body or X-chromatin Barr body is found attached to nuclear envelops in oral mucosa, any where in the nucleus in nerve cells and as drumstick or small rod at one side of nucleus in neutrophil or polymorphonuclear leucocytes (Davidson and Smith) Barr body is produced due to partial inactivation of one X-chromosome and development of facultative heterochromatin in it. Any of the two X-chromosomes can become heterochromatic. It begins in the late blastocyst stage (roughly 16 day of embryonic life). Partial inactivation of one X-chromosomes in females is called Dosage compensation