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

question 18

Multiple Choice

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