The ability to roll the tongue is caused by a dominant allele. A woman is a "roller," but one of her parents is not. The woman is expecting a child with a man who is a "nonroller." What is the probability that their first child will be a "roller"?
A) 1/4
B) 0
C) 3/4
D) 1/2
E) 1

Question

Quizplus · Accepted Answer

The woman must be heterozygous (Rr) because she is a roller but has a nonroller parent (rr). The man is a nonroller (rr). The possible genotypes for their child are Rr (roller) and rr (nonroller), giving a 1/2 probability of being a roller.

The Ability to Roll the Tongue Is Caused by a Dominant