Maddie receives the brown-eyed allele of the eye-color gene from her mother, but the blue-eyed allele of the eye-color gene from her father. maddie is for the eye-color gene.

Heterozygous

The term heterozygous is used to describe individuals that possessive two different alleles for a given gene. In this case, for the gene controlling eye color, Maddie is heterozygous because Maddie has alleles for both blue colored eyes as well as brown colored eyes. The opposite of such individuals are homozygous individuals, which have the same allele for a specific gene.