The dystrophy is caused by an abnormal gene on the X chromosome. Males have on X and one Y chromosome, so that if the X chromosome is abnormal, then he will develop the dystrophy. In contrast, females have two X chromosomes, and if one of them is abnormal, then she will not show signs of dystrophy, but will be a carrier. For a carrier, each of her sons will have a 50% chance of inheriting the abnormal gene and be affected, while each daughter will have a 50% chance of being a carrier.
I have been told Duchenne muscular dystrophy is an X-linked disorder. What does this mean?