Mary is heterozygous for blue eyes, a recessive trait. John is homozygous for brown eyes, a dominant trait. What color eyes will their four children have?
A) Brown
B) Blue
C) Some will have blue, and some will have brown
D) Impossible to tell

Question

Quizplus · Accepted Answer

A heterozygote with a dominant and a recessive allele will have the dominant phenotype. In Mary's case, this will manifest itself in her brown eyes. A homozygote with two dominant alleles will have the dominant phenotype, so John also has brown eyes. To have blue eyes, the children would have to inherit two alleles for blue eyes. Because they will inherit, at most, one recessive allele for blue eyes, the children's eyes will be brown.

Mary Is Heterozygous for Blue Eyes, a Recessive Trait