Question

Sickle cell disease (sickle cell anemia) is a relatively common disorder in individuals of African descent and affects approximately 1 in 500 African-Americans. Due to a mutation in an autosomal gene for hemoglobin, the homozygous recessive genotype leads to red blood cells that are relatively stiff and sticky, and deform into a sickle shape as they lose oxygen. This leads to problems in the spleen, and anemia. There are hundreds of different hemoglobin alleles. Individuals heterozygous for the sickle cell allele and one non-sickle cell allele usually do not experience major complications or even noticeable symptoms. A genetic test is available to diagnose carriers. Mitchell does not have sickle cell disease, neither does his mother or father, but his sister does. His wife Darlene does not have sickle cell disease, and neither of her parents do either. Darlene also has a sister who has sickle cell anemia and two brothers without the disease.

Question: If Mitchell and Darlene have a child, what is the probability that the child would be a heterozygote carrier of the recessive allele? You may draw the Punnett square but please solve the problem using probability calculations, then explain your reasoning in 2-5 complete sentences.

Answer 1

Mitchell and Darlene both have sickle cell anemic siblings,it confirms that their parents must be heterozygous carrier for the disease.

The probability of Mitchell and Darlene being heterozygous carrier is more in comparision to to being normal.

Now if they get married,the probability of having heterozygous carrier progeny will be 1/2.

We can draw the punnet square to get this