Question

In a human female, a test is conducted to test for the presence of a particular protein. The protein is expressed in skin fibroblast cells.   Small samples of skin fibroblast cells are removed from different parts of the female's body. It is found that in skin fibroblast samples taken from some parts of her body, only a mutant form of the protein is expressed. In other skin fibroblast samples, taken from other parts of her body, only the wild type form of the protein is expressed. Explain why this female shows this pattern of expression.

Answer 1

This pattern is expressed because of X- inactivation in females.

One of the x-chromosomes from the females are inactivated to balance the production to males for continuity in species.This is because the males have only one X chromosome as compared tot the female having 2.This is done to prevent the double dose.

Thus, one is activated only. But this happens at early stage in embryo as a result , some cells of the body inactivate one x chromsomes and some deactivate other X- chromsome resulting in a mosaic in the female body of allele expressed.

This is also seen in Calico cats.