Having polydactyly (extra digits on hands and feet) is a dominant trait. A man has polydactyly. His wife and oldest daughter do not have polydactyly. The couple's second child has polydactyly. What is the probability that their next (third) child will have extra digits?
A) 1/2
B) 1/16
C) 1/8
D) 3/4

Question

Quizplus · Accepted Answer

Since polydactyly is a dominant trait, the man must have at least one allele for polydactyly. His wife, not having polydactyly, must have two recessive alleles. Therefore, each child has a 1/2 chance of inheriting the dominant allele from the father.

Having Polydactyly (Extra Digits on Hands and Feet) Is a Dominant