As a genetic counselor, you advise couples about the possibility of genetic disease in their offspring. This morning you met with an engaged couple, both of whom are phenotypically normal. The man, however, has a brother who died of Duchenne-type muscular dystrophy, an X-linked condition that results in death before the age of 20. The allele responsible for this disease is recessive. His fiancee, whose family has no history of the disease, is worried that the couple's sons or daughters might be afflicted. Requied:
a. How would you advise this couple?
b. The sister of this man is planning to marry his fiancée's brother. How would you advise this second couple?