Question

Sickle cell anemia is a genetic disease caused by a recessive allele. Sickle cell anemia affects the hemoglobin in red blood cells, making them the shape of crescents instead of disks. The disease can cause pain and damage blood vessels.

A genetic counselor meets with a man and a woman that both are carriers of sickle cell anemia. Carriers have one copy of the sickle cell allele and one copy of the allele for making normal hemoglobin.

What is the probability that the couple would have a child that was also a carrier for sickle cell anemia?

0%

25%

50%

75%

100%

Answer 1

50%

Explanation: With two carriers (genotypes Aa × Aa), the Punnett square gives AA (25%), Aa (25%), aA (25%), aa (25%). The heterozygous children (Aa or aA) are carriers, totaling 50%.