Sanjay and Indira have thalassemia minor.Their young daughters are dizygotic (fraternal)twins.Malonie has thalassemia minor like her parents,but Jewel has the more severe thalassemia major.The more serious case most likely arose because

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Thalassemia is an autosomal recessive disorder, meaning that it is caused by inheriting two copies of a recessive mutant allele. Sanjay and Indira both have thalassemia minor, which means they each have one recessive mutant allele and one wild type allele for the beta globin gene. When they had twins, there was a 25% chance for each of their children to inherit two mutant alleles and therefore have thalassemia major. Jewel inherited two recessive mutant alleles, which caused her to have the more severe thalassemia major. Option A is incorrect because Jewel did not inherit any wild type alleles for the beta globin gene. Option B is incorrect because thalassemia is not inherited in a dominant fashion. Option D is incorrect because sickle cell disease is a different genetic disorder than thalassemia.

Sanjay and Indira Have Thalassemia Minor