Unattached earlobes are a dominant trait. Finn and Maggie both have unattached earlobes but their daughter, Celia, does not. If Finn and Maggie have a second child, what is the probability that it will have attached earlobes?
A) 1/4
B) 1/2
C) 3/4
D) 1
E) 1/8

Question

Quizplus · Accepted Answer

Unattached earlobes (U) are dominant, and attached earlobes (u) are recessive. Finn and Maggie must both be heterozygous (Uu) since they have a child with attached earlobes (uu). The probability of their second child having attached earlobes is 1/4, as shown by the Punnett square: Uu x Uu results in 1/4 chance of uu.

Unattached Earlobes Are a Dominant Trait