Question

Number of Barr bodies in XXXX females would be
A) 4
B) 3
C) 2
D) 1

Answer 1

Hint: Among the 46 chromosomes, 44 chromosomes are related to phenotypic inheritance only 2 chromosomes are involved in genotypic inheritance.

Complete Answer:
- In humans, we have 23 pairs of chromosomes; among these 22 pairs are autosomes while one pair is termed as sex chromosome. This one pair helps in determining the sex of an individual.
- In humans females have 2X chromosomes that they received from each parent and males have one X and one Y chromosomes that they receive from each of the parents.
- Now, Barr body is an inactive X chromosome that becomes super coiled to heterochromatin in early embryogenesis.
- It is related to dosage compensation, in females, one of the X chromosomes is inactivated. This is because both male and female have only one functional X chromosome in each cell, the male has only one X chromosome but females have two X chromosomes that means they have a gene for X chromosome twice in number.
- Thus the number of Barr bodies is always one less than the total number of X chromosomes present, therefore, if a female has XXXX means 4 X-chromosome she will have three Barr bodies.

Thus the correct answer is ‘B’ i.e 3.

Note: Klinfelter’s syndrome and Turner’s syndrome are the sexual disorders cause due to addition and deletion of sex chromosomes. In klinefelter male, they have XXY chromosomes that mean they have one Barr body per cell. In turner syndrome, they have XO chromosome they have absence of X chromosome no Barr body is there.