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.

Option A, Homozygous for

Explanation:

Options for the question are

a)Homozygous for

b)Heterozygous for

c)A carrier of  

d)A recessive of

Solution

Given

Both the parents have allele for brown hair.

Let the allele for brown hair be "b"

Since both the parents are carrier of this allele , it is hence sure that allele "b" is recessive.

Now , let us assume that the dominant allele (for any other hair color) be "B"

Since parents are carrier they must be having heterozygous genotype i.e Bb

Now when two Bb parents are crossed the following offspring are produced

Bb * Bb

BB, Bb, Bb, bb

here only offspring bb will have brown hair, while offspring Bb will be carrier just like their parents and BB will the dominant trait color

Hence, for expression of brown hair color trait, it is compulsory for the offspring to be homozygous for the trait,

Thus, option A is correct