Case Study 1  Marsha and Clement are both carriers of sickle cell disease, a disease that is autosomal recessive. Their first child, Amelia, does not have the disease. Marsha and Clement are planning another pregnancy, but they are concerned about their second child having the condition. Clement’s dad died from complications of sickle cell disease shortly before Amelia was born.  1.Draw a Punnett square to determine the likelihood of Marsha and Clement having a baby with sickle cell disease. What is the chance the baby will be a carrier of the disease, just like the parents? 2.Marsha suggested to the nurse at the local family planning clinic that if the baby were a boy he might have a higher risk for developing the disease, just like his grandfather. If you were this Practitioner, how would you respond? 3.When Amelia, who does not have sickle cell disease, grows up and marries someone who does have the disease, how likely is it that her children will have the disease?

1. Punnett Square Analysis:
To determine the likelihood of Marsha and Clement having a baby with sickle cell disease, we can use a Punnett square. Sickle cell disease is an autosomal recessive condition, meaning that both parents must be carriers of the disease in order for the child to have the disease.

Let’s represent the alleles for the sickle cell gene as H (normal hemoglobin) and h (sickle cell hemoglobin). Marsha and Clement are both carriers, so they each have one normal allele (H) and one sickle cell allele (h).

Using a Punnett square, we can cross Marsha’s and Clement’s alleles to determine the possible genotypes of their offspring:

H h
——————
H | HH Hh
——————
h | Hh hh

From the Punnett square, we can see that there is a 25% chance that their baby will have sickle cell disease (hh genotype), as both parents must pass on the sickle cell allele. Additionally, there is a 50% chance that the baby will be a carrier (Hh genotype), inheriting the sickle cell allele from one parent. Lastly, there is a 25% chance that the baby will have no copies of the sickle cell gene (HH genotype).

2. Responding to Marsha’s Concern:
If Marsha suggests that a male child has a higher risk for developing sickle cell disease, just like his grandfather, as a practitioner, it is essential to provide accurate information. In the case of sickle cell disease, gender does not play a role in determining the risk of developing the disease.

Sickle cell disease is inherited in an autosomal recessive manner, meaning that both males and females have an equal chance of developing the disease if they inherit two copies of the sickle cell allele. The risk is not higher for males specifically. To address Marsha’s concern, I would explain that the risk of developing sickle cell disease depends solely on whether the child inherits two sickle cell alleles, regardless of their gender.

3. Likelihood of Amelia’s Children Having the Disease:
Amelia does not have sickle cell disease, but we know that she is a carrier since both Marsha and Clement carry the disease. When Amelia grows up and marries someone who has the disease, the likelihood of her children having sickle cell disease can be determined using the Punnett square again.

Since Amelia is a carrier (Hh genotype), she has a 50% chance of passing on the sickle cell allele to her offspring. If her partner has sickle cell disease (hh genotype), there is a 50% chance that their child will inherit the sickle cell allele from Amelia. Thus, the probability of Amelia’s children having sickle cell disease is 0.5 multiplied by 0.5, which is 0.25 or 25%.

In summary, Marsha and Clement have a 25% chance of having a baby with sickle cell disease, and a 50% chance of having a baby who is a carrier. The risk of developing sickle cell disease is independent of gender. If Amelia marries someone with the disease, there is a 25% chance that their children will have sickle cell disease.