A Family with Only One Affected Parent and a Child

Multiple Choice

A family with only one affected parent and a child with a dominant disease would like to know what the probability is that one of their unaffected children might be a carrier. What do you tell them?

A) the chance that an unaffected child is a carrier is 50%
B) the chance that an unaffected child is a carrier is less than 50%
C) the chance that an unaffected child is a carrier is 0%
D) the chance that an unaffected child is a carrier is 75%
E) the chance that an unaffected child is a carrier is 2/3