Question

How can the inactivation of one X chromosome in every XX female cell during early embryogenesis lead to females with mild forms of X-linked recessive genetic disorders?

Answer 1

X chromosome is one of sex chromosome other than Y chromosome which is found in males only. There are 2 copies of X chromosome in any female. Women do need only one of the X chromosome so the other X chromosome is shut down, this is called X inactivation. In X inactivation the one X chromosome is condensed and they make the Barr body. In Barr bodies the genes are not active so all the information is conveyed by one X chromosome.

X linked diseases are severe to males because they only have only one copy of X chromosome and if genes are inactivated at any point because of any mutation they are susceptible for such X-linked disease. Though there are comparatively very little chance in females to have X chromosome linked diseases because of presence of 2 copies. But some might carry 3 X chromosome which might cause problem if not inactivated. Females with XXX chromosome are fertile but they might be incapable of learning and engage in normal conversation.