Question

1. brown eyes are dominant to blue eyes. if two brown eyed individuals have a child with blue eyes, that means: a. both parents are homozygous for brown eyes. b. both parents are heterozygous. c. one parent is homozygous and the other is heterozygous. d. there is a 75% chance that their second child will have blue eyes. e. there is a 100% chance that their second child will have brown eyes.

Explanation:

Brown eyes (B) are dominant over blue eyes (b). For two brown - eyed parents to have a blue - eyed child (bb), each parent must carry the recessive allele. So they must be heterozygous (Bb). If they were homozygous dominant (BB), they couldn't pass on the recessive allele. The probability of their second child having blue eyes is 25% (from a Bb x Bb cross: 1BB:2Bb:1bb), and having brown eyes is 75%.

Answer:

B. Both parents are heterozygous