Observations on the So-Called Sex Chromatin in Man

Abstract

SUMMARY The difference in nuclear structure between male and female tissues in man has been examined in liver tissue from three embryos of each sex. The so-called sex chromatin consists of a large heterochromatic segment of the X chromosome, thus existing in duplicate in female diploid cells. The two segments have a tendency of juxtaposition resulting in a larger heterochromatic body in female than in male cells. Beside the large heterochromatic segment the X chromosome has, in the tissues studied, a euchromatic segment attached through a small terminal heterochromatic knob to a nucleolus. In male cells the euchromatic segment of the X chromosome is often joined terminally to a small heterochromatic segment believed to belong to the Y chromosome.