Question

Where are Barr bodies found?
A. Ova
B. Sperms
C. Somatic cells of man
D. Somatic cells of woman

Answer 1

The Barr bodies are also referred as sex chromatin. In addition to it, the knowledge of the X chromosome is needed to answer the above question. A cell with two X chromosomes consists of one inactive chromosome.

Complete step by step answer: In a cell with more than one X chromosome, an inactive X chromosome is found. This inactive X chromosome is called the Barr body. In species with XY sex-determination which also includes humans, the X chromosome is inactivated by a process called lyonization. According to the Lyon hypothesis cells with multiple X chromosomes, one is inactivated during mammalian embryogenesis. Human females consist of two X chromosomes, while males have one X chromosome and one Y chromosome. Somatic cells are the one which does not take part in sexual reproduction. one of the X chromosomes of a female is active, and the other is inactivated. One of the X chromosomes is inactivated so that only the necessary amount of genetic information is expressed. Expression of genes must be equal in both males and females therefore inactivation of one X chromosome takes place in somatic cells of females. Inside the nucleus of neutrophils, at the rim of the nucleus, barr bodies are seen in the female somatic cells.
So, option D is the right answer, i.e., a barr body that is inactivated X chromosome is found in the somatic cell of a woman.

Note: No Barr body is found in the somatic cell of the male because males consist of only one X chromosome, but it is not present in the gametic cell (sperm). In breast cancer, the patient’s reactivation of the Barr body is seen.