John and his grandmother are both homozygous for alkaptonuri…
John and his grandmother are both homozygous for alkaptonuria, an autosomal recessive disease. John’s grandmother has two brothers and a sister. One of the brothers had alkaptonuria and his daughter is John’s mother. If John’s parents decide to have another child, what is the probability of the child to be affected with alkaptonuria? Select the right answer and write your calculations on your scratch paper for credit.