A man has extra digits (six fingers on each hand and six toes on each foot). His wife and their daughter have a normal number of digits. Having extra digits is a dominant trait. The couple's second child has extra digits. 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
E) 9/16

Question

Quizplus · Accepted Answer

Since having extra digits is a dominant trait and the man has extra digits while his wife does not, the man must be heterozygous (Hh) to have produced a child with a normal number of digits with his wife, who must be homozygous recessive (hh). Therefore, each child has a 1/2 chance of inheriting the dominant allele (H) from the father and thus having extra digits.

A Man Has Extra Digits (Six Fingers on Each Hand