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

the gene encoding the protein is present on the X chromosome, and the female is heterozygous for this gene.

For dosage compensation X chromosome inactivation occurs in females, it occurs in the early embryonic stages and X chromosome inactivation is random any one the X chromosome can be inactivated and the cell should have only one active X chromosome. Those cells which have X chromosome with the functional allele for the gene in the active state divide to produce cells which has the same X chromosome in the active state.

so those cells which produce functional protein has the X chromosome which has functional allele in the active state and those cells which produce mutant protein has the X chromosome which has mutated allele in the active state.