Question

The number of Barr body in XXXX female is
A. 1
B. 2
C. 3
D. 4

Answer 1

The Barr bodies are the inactive X chromosomes that are tightly coiled into the heterochromatin at the early stage of embryogenesis. They are related to dosage compensation in females. This is accomplished by the inactivation of one X chromosome from the total number of chromosomes.

Complete step-by-step answer:
Barr bodies are small structures that are present in the nuclei of the cells of the females. They consist of an inactive X chromosome along with another X chromosome in a cell. Therefore, the total number of Barr bodies is always one less than the total number of X chromosomes present. This is done to ensure that both the female and male have only one functional X chromosome present per cell.
The human females have the XX genotype. This means that they have two X chromosomes present in their cells so twice the genes of the X chromosome present. So, their total number of Barr bodies is one. This is because the total number of Barr bodies is calculated as one less than the total number of X chromosomes. So, one less than two is one. Similarly, human males have the XY genotype. This means that they have one X chromosome present in their cells. So, their total number of Barr bodies is zero. This is because the total number of Barr bodies is calculated as one less than the total number of X chromosomes. So, one less than one is zero.
A female with XXXX genotype has four X chromosomes. Now the total number of Barr bodies will be three. This is because the total number of Barr bodies is calculated as one less than the total number of X chromosomes. So, one less than four is three.
Thus, based on the above information we can conclude that the number of Barr bodies in XXXX female is 3.

Hence, the correct answer is an option (C).

Note: Barr bodies are used for sex determination. The sex of the unborn fetus is determined by checking the presence of the Barr bodies in the amniotic fluid. If the amniotic fluid contains no Barr bodies then the child is male otherwise female.