Question

What is the probability that a women carrying an abnormal X-linked gene has two sons unaffected an one affected? 

Answer 1

A woman who is a carrier of an X-linked recessive disorder has a 25% chance of having an unaffected son, a 25% chance of having an affected son, a 25% chance of having an unaffected daughter and a 25% chance of having a daughter who also is a carrier.