7a) In the American population of immigrants from southern Italy, mutations in t

Question

7a) In the American population of immigrants from southern Italy, mutations in the hemoglobin genes that predispose to a person thalassemia are common. Why are people from a warmer Mediterranean climate more likely to show hemoglobin mutations?

7b) A couple who are both from Sicily would like to marry and start a family. The woman has been advised by her parents that she had a brother with -thalassemia that died before she was born. Her soon-to-be husband has a sibling with -thalassemia trait. Should this couple be concerned about having a child with thalassemia? What is the likelihood that a child from this couple would be affected by thalassemia?

Explanation / Answer

7a. The warmer Mediterranean climate means that malaria is prevalent there. Thalassemia is common here because it helps to protect thalassemia carriers from malaria. The malarial parasite replicates in the RBCs and feeds on the hemoglobin.The altered hemoglobin in thalassemia carriers protects their RBCs from invasion or replication of the malarial parasite.

7b) Thalassemia is usually inherited in an autosomal recessive manner. The siblings of a patient with an autosomal recessive disease have about a 25% chance of being affected with the same disease and a 50% chance of being carriers. Thalassemia carriers are normally healthy and do not know that they are carriers.

If both the lady and the man are carriers then they need to be concerned about having a child with thalassemia. The probability that they will have a child with thalassemia is 25%.

However, if only one of them is a carrier, then they need not worry about having a child with thalassemia, but there will be a 50% chance that the child will be a carrier.

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