, Volume 3, Issue 3, pp 189-234

Hemoglobin E: Distribution and population dynamics

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Abstract

Hemoglobin E, an anomaly of the β-chain of human hemoglobin, is widely distributed in Southeast Asia and adjacent areas. In some populations of Southeast Asia the frequency of the gene responsible for the production of HbE reaches values near 0.3. In view of the probable disadvantage of the HbE homozygote and the certain disadvantage of the double heterozygote for the HbE and β-thalassemia genes an advantage of the heterozygote has to be postulated in order to explain the high gene frequencies. There is some evidence for and against malaria protection being the factor conveying heterozygote advantage. Data concerning genotype fitnesses in the triallelic system involving HbA, HbE and β-thalassemia are scanty. Crude fitness data based on clinical observations and equilibrium calculations indicate that the system is unstable. Dynamic models of the three genes suggest that the HbE gene is replacing the β-thalassemia gene in most Southeast Asian populations. The distribution of HbE and that of the austroasiatic group of languages are similar. This and several other aspects of the geographic and ethnic distribution of HbE are discussed in the last section of this review.