Bill has come to you for genetic counseling.  He isconcerned that he and his sister (Alice) are at risk for Huntingtondisease. Bill and Alice are too young to showsymptoms.  Their grandmother, (Mary) had Huntingtondisease.  Her three children, Shirley, Tom, and Ed so farshow no symptoms.  Shirley is the oldest (45 years old)and is Bill and Alice’s mother. A study by Adams (American Journalof Human Genetics 43;695 – 704, 1988) indicates that 68% ofindividuals heterozygous for the Huntington allele show symptoms byage 45.  Â
a. Draw a pedigree of this family.
b. What is the probability that Bill is heterozygous forHuntington disease?
c. What test(s) would you recommend for Bill and Alice todetermine if they are heterozygous?
d. Explain why you recommend this test, what results it cangive, and how these results can answer Bill’s question.
