Huntington disease is a rare fatal, degenerative neurological disease in which individuals start to show symptoms, on an average, in their 40s. It is caused by a dominant allele. Joe, a man in his 20s, just learned that his father has Huntington disease.
a. What is the probability that Joe will also develop the disease?
b. Joe and his new wife have been eager to start a family. What is the probability that their first child will eventually develop the disease?