. A child with very low blood oxygen levels was given a test for alpha thalassem
ID: 62312 • Letter: #
Question
. A child with very low blood oxygen levels was given a test for alpha thalassemia The test was a Northern blot test using a standard probe that binds to alpha globin mRNA. The resulting Northern blot had three bands, indicating the child has three different sizes of alpha globin mRNA molecules. One is normal size, one is larger than normal, and one is smaller than normal. The parents of the patient are both from Mediterranean countries but there is no reasonable chance that they are related.
a). Give one possible mutant genotype that the child might have that would result in her forming three different sized alpha globin mRNA molecules, and explain how this genotype would also cause her to have low blood oxygen levels.
b). What test would you do to confirm your hypothesis?
c). Predict what results you would expect from your test if your hypothesis is correct
Explanation / Answer
a. The child might have a deletion of one of the 4 genes coding for 1 of the 4 alpha proteins. In the remaining 3, two are mutated. Hence, they are non functional. This causes the anemia in the child because the concentration of alpha proteins need to be present to carry oxygen to the tissues. If beta chains become more in number when compared, it causes anemia. This is because beta chains have more affinity for oxygen and prevent dissociation of oxygen in tissues. This causes tissues to lose oxygen supply.
b. The tests we can do to confirm:
DNA analysis can be done on the parents to check if they are carriers. Other tests include peripheral smear, complete blood count, hemoglobinopathy evaluation.
In CBC, a low MCV is an indication of thalassemia. In the blood smear, we can see paler and smaller RBC. In hemoglobinopathy evaluation, the type of hemoglobin in the cell is measured.
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