What are the possible genotypes of the parents?

Muscular Dystrophy is caused by an X-Linked recessive pattern. In order for a male to receive the disease, the trait has come from the mom. It's impossible for the just father to pass down the trait to his son. Now he can pass it to his daughter. If a mother is carrier of the disease, meaning she is affected on one chromosome, and the father is normal, it's a 50%  chance that the their son will inherit the disease. Their daughter has a 50%  chance of carrying the trait, but not actually having it. Now if the dad has the disease and the mom is a carrier, it's a 100% the the daughter will inherit the trait; 50% that she'll be a carrier and 50% acquire the disease. As for the son, he, again, has a 50% chance of having the disease. If both parents have full blown Muscular Dystrophy (their both affected, not carriers), then it's a 100% chance that both the boy and girl will have the disease.