Huntington’s disease, an often fatal disease of the central nervous system, is inherited from a dominant allele. Furthermore, a person may not show symptoms of the disease until 30 – 50 years of age. Jack and Jill have been married for 40 years and have two children, Joe and Jane. Jack has recently been diagnosed with Huntington’s disease. Assuming that Jane does not have the disease, determine the probability that one of the children will eventually have Huntington’s. What is the probability that both Joe and Jane will inherit the disease?
Explain how females with the chromosome constitution XXX are often fertile with normal intelligence and lead normal lives.