The square above is based on the eye color of two parents, one of whom has brown eyes and carries the recessive gene for green eyes (a). What is the probability that a biological child of these parents will have brown eyes?

In the Punnett Square pictured, two of the children have brown eyes(A) and carry the recessive green gene(a) = (Aa), while two of the children have green eyes (aa). There is a 50% chance these parents will produce offspring with brown eyes (Aa).