In humans, the allele for brown eyes (B) is dominant to the allele for blue eyes (b). What is the probability that two heterozygous brown-eyed parents will have a child with blue eyes?

Question

B b
B ? ?
b ? ?
A.
50%
B.
0%
C.
25%
D.
75%

Answer 1

The two parents are heterozygous (Bb) for eye color. When they have a child, there is a 25% chance that they will pass on the recessive allele for blue eyes (b) to that child. Therefore, the probability that two heterozygous brown-eyed parents will have a child with blue eyes is 25%, so the answer is C. 25%.