Evidence of Selection for the α-Globin Gene Deletions and Triplications in a Southern Chinese Population.

α(+)-Thalassemia (α(+)-thal) is common in Southern China. The high frequency could be due to over dominant selection through malaria. Two molecular mechanisms that produce α(+)-thal have been defined; one results in the -α(3.7) (rightward) deletion and reciprocal ααα(anti 3.7) triplication, and the other one results in the -α(4.2) (leftward) deletion and reciprocal ααα(anti 4.2) triplication. Considering that each de novo event produced a chromosome with an α gene deletion and a chromosome with an α triplication, if there is no favorable allele, one would expected to find the same allelic frequencies. We found a favorable selection for the -α(3.7) deletion in the Chinese population, and we also found that the α triplication is not as rare as was first thought, especially for the ααα(anti 3.7) triplication.