Maddox and Maecy both carry alleles for brown hair. Their 4-year-old son, Drake, also has brown hair. Therefore, Drake is ______ the trait of brown hair.

Question

Quizplus · Accepted Answer

Since both Maddox and Maecy carry alleles for brown hair, they are most likely heterozygous (Bb) for the trait. When they had a child, there was a 25% chance of their child being homozygous dominant (BB), a 50% chance of their child being heterozygous (Bb), and a 25% chance of their child being homozygous recessive (bb). The fact that their child has brown hair indicates that he has inherited at least one dominant allele from one or both of his parents, which means he is either homozygous dominant (BB) or heterozygous (Bb). Since there is no information to suggest that he received a recessive allele from either of his parents, he cannot be homozygous recessive (bb). Therefore, the best answer is that Drake is homozygous for the trait of brown hair (choice A).

Maddox and Maecy Both Carry Alleles for Brown Hair