Question

In the human female, Barr bodies are formed by,
A. Inactivation of mother’s X chromosome
B. Inactivation of father’s X chromosome
C. Inactivation of both father’s and mother’s X chromosome
D. Inactivation of either mother’s or father’s X chromosome

Answer 1

Hint:- we have to think about the genetic disorder that occurs during the time of recombination of cell cycle .It is described in details in human health and disease chapter class 12th.it indicating the X chromosome presence.

Complete Answer:-As in the time of crossing of gene expression the result of X inactivation is that all normal females are mosaics with regards to this chromosome.
So a barr body is an inactive X chromosome in a cell with more than one X chromosome, rendered inactive in a process is called lyonization. It is discovered by Murray Barr.In process of XY sex determination, it was discovered. The Lyon hypothesis states that in the cell with multiple X chromosomes, all but one are inactivated during mammalian embryogenesis.This happens early in embryonic development, except in marsupials and in some extraembryonic tissue of some placental mammals, in which the x chromosomes from the sperm is always deactivated.But in case of us i.e. human beings it is inactivated either from male gamete or female. So after zygote, if it male, then no Barr body
 If it is female, then one Barr body
The determining mathematical expression is,
 No. of Barr body = (n-1) where n= no. of X chromosome
In Klinefelter syndrome XXY, Barr body =1
  Turner syndrome X0, Barr body= 0

So from above, D is the correct option.

Note:- As it is a database question we have read chapter thoroughly and answered this question, as per this question we also solve as we know in maximum case, at the time of crossing all characters come from either male or female.