From SNPedia
| Genotype | Effect |
|---|
| rs334(T;T) | sickle cell anemia |
| rs334(A;T) | carrier of, but unaffected by, sickle cell anemia; greater malaria resistance |
| rs334(A;A) | normal allele |
The most common allele of rs334 is (A), encoding the Hb A form of (adult) hemoglobin. rs334(T) encodes the sickling form of hemoglobin, Hb S. Only individuals homozygous for this allele, in other words having the rs334(T;T) genotype, will have sickle cell anemia. The (T) allele appears to have maintained through evolution due to the ~10 fold higher resistance to life-threatening forms of malaria that heterozygotes (rs334(A;T) genotypes) exhibit.
See the SNPedia sickle cell anemia entry for more information.
| ? | (A;A) (A;T) |
|---|
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[PMID 20128890] Loss of balancing selection in the betaS globin locus
