Polydactyly is expressed when an individual has extra fingers and/or toes.Assume that a man with six fingers on each hand and six toes on each foot marries a woman with a normal number of digits.Having extra digits is caused by a dominant allele.The couple has a son with normal hands and feet,but the couple's second child has extra digits.What is the probability that their next child will have polydactyly?
A) 1/32
B) 1/8
C) 7/16
D) 1/2
E) 3/4

Question

Quizplus · Accepted Answer

Since polydactyly is caused by a dominant allele and the man has polydactyly, his genotype must include at least one dominant allele (let's denote the dominant allele as "P" and the recessive allele as "p"). Given that they have a son with normal hands and feet, the man must be heterozygous (Pp) because he passed a recessive allele to this son. The woman has normal digits, so her genotype is pp. The possible genotypes of their children are Pp (polydactyly) and pp (normal), each with a probability of 1/2. Therefore, the probability that their next child will have polydactyly is 1/2.

Polydactyly Is Expressed When an Individual Has Extra Fingers And/or