In humans,the sickle-cell trait is caused by a single defective allele,but sickle-cell disease only occurs in individuals that are homozygous for the sickle-cell allele.A man and woman each carry the trait,but do not have sickle-cell disease.What is the probability that their first two children will both have sickle-cell disease?
A)1/16
B)1/8
C)1/4
D)3/8
E)1/2

Question

Quizplus · Accepted Answer

Since both parents are carriers (heterozygous) for the sickle-cell trait, each child has a 1/4 chance of being homozygous for the sickle-cell allele and thus having sickle-cell disease. The probability that both of two children will have the disease is (1/4) * (1/4) = 1/16.

In Humans,the Sickle-Cell Trait Is Caused by a Single Defective