Question

The number of Barr bodies found in a female with XXX chromosomes will be _____.

• A. four
• B. three
• C. two
• D. one

Answer 1

The correct option is C two

A Barr body is an inactivated, condensed X chromosome found in the nucleus of female somatic cells which is between divisions. Barr body is formed when an X chromosome is compacted into a dense and small body where the genes remain inactivated. The reason for shutting off one X chromosome is so that only the necessary amount of genetic information is expressed, rather than double or even more. In short, the amount of X chromosome genes expressed has to be equal in both males and females.
The number of Barr bodies in a cell is one less than the number of X chromosomes. For example:
In a normal female with the genotype 46, XX (or 44+XX), the number of Barr bodies would be 1.
In a normal male with the genotype 46, XY (or 44+XY), the number of Barr bodies would be 0.
Therefore, the number of Barr bodies in females with XXX will have two Barr bodies.