Kaplan Nursing Entrance Practice Exam

Individuals with a homozygous bb genotype have which eye color?

1. Brown

2. Blue

3. Green

4. Gray

The correct answer is: Blue

Individuals with a homozygous bb genotype typically have blue eyes because the genotype "bb" represents two recessive alleles. In the context of eye color genetics, brown eyes are dominant over blue and other colors. Therefore, to express the blue eye color phenotype, an individual must inherit two copies of the recessive allele (bb). The presence of a dominant allele for brown eyes (represented as a capital 'B') would override the recessive 'b' alleles, resulting in brown eyes, which explains why individuals with at least one B allele would not have blue eyes. Consequently, only individuals with the recessive homozygous bb genotype can express blue eyes. This genetic principle is part of Mendelian inheritance, where dominant and recessive traits determine physical characteristics.