Torey and Bill consult a geneticist regarding the risk that their baby will inherit sickle-cell disease. They are told that Torey carries the affected allele and Bill does not. What does this mean?
A) There is a 25% chance the baby will inherit sickle cell trait, and no chance of inheriting the disease.
B) There is a 100% chance the baby will inherit the sickle cell disease.
C) There is a 50% chance the baby will inherit sickle cell trait, and no chance of inheriting the disease.
D) There is a 25% chance the baby will inherit sickle cell trait, and a 25% chance of inheriting the disease.

Question

Quizplus · Accepted Answer

Torey is a carrier for the sickle-cell allele, meaning she has one copy of the normal allele and one copy of the sickle-cell allele. Bill does not carry the sickle-cell allele. Therefore, each of their children will inherit one copy of the normal allele from Bill, and one copy of either the normal or sickle-cell allele from Torey. There is a 50% chance the baby will inherit the sickle-cell allele from Torey and be a carrier like her, but there is no chance the baby will inherit two copies of the sickle-cell allele and develop the disease. Therefore, the baby has a 50% chance of inheriting sickle-cell trait and a 50% chance of inheriting only normal alleles.

Torey and Bill Consult a Geneticist Regarding the Risk That