An unexpectedly high frequency of heterozygosity for alpha-thalassemia in Ashkenazi Jews

Blood Cells Mol Dis. 2004 Jul-Aug;33(1):1-3. doi: 10.1016/j.bcmd.2004.04.009.


alpha-Thalassemia is among the world's most common single gene disorders, which is most prevalent in the malaria belt. This geographic distribution has been attributed to a selective advantage of heterozygotes against this disease. Unexpectedly, we have found a high frequency of heterozygosity for deletional alpha-thalassemia (-alpha3.7) in Ashkenazi Jews (carrier frequency of 7.9%, allele frequency of 0.04). This population has resided in temperate climates for many centuries and was therefore not subjected to malarial selection pressure. In comparison, heterozygosity for beta-thalassemia, which is highly subject to malarial selection pressure, is very low (estimated <0.1%) in this group. It is possible that founder effect and genetic drift have contributed to the high frequency of deletional alpha-thalassemia in Ashkenazim, as may occur in closed populations. Alternatively, we hypothesize that positive selection pressure for an as yet unknown linked allele on chromosome 16 may be a significant factor leading to this high frequency.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Founder Effect
  • Gene Deletion*
  • Gene Frequency
  • Genetic Carrier Screening
  • Genetic Drift
  • Genetic Linkage
  • Heterozygote*
  • Humans
  • Jews / genetics
  • Molecular Epidemiology
  • Selection, Genetic
  • alpha-Thalassemia / epidemiology
  • alpha-Thalassemia / ethnology*
  • alpha-Thalassemia / genetics*