Question

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 three additional children will have polydactyly?

a.1/8
b.1/32
c.7/16
d. 3/4
e. 1.2

Answer 1

The probability that their next three additional children will have polydactyly is 1/8.

Step-by-step explanation:

The probability that the next three additional children of the couple will have polydactyly can be determined using Punnett squares. Since the man has the dominant allele for polydactyly (P) and the woman has the normal allele (p), their genotypes are Pp and pp, respectively. When crossed, the possible genotypes of their children are Pp and pp with equal probabilities. Therefore, the probability that their next child will have polydactyly is 50% or 1/2. Since the occurrence of polydactyly is independent in each child, the probability that all three additional children will have polydactyly is (1/2)^3 = 1/8.