EXTREMELY HIGH-FREQUENCIES OF ALPHA-GLOBIN GENE DELETION IN MADANG AND ON KAR-KAR ISLAND, PAPUA-NEW-GUINEA

  • 1 January 1985
    • journal article
    • research article
    • Vol. 37  (4) , 778-784
Abstract
Extremely high frequencies of the deletion form of .alpha.+ thalassemia (-.alpha./), as studied by the DNA mapping technique, were found in the population of Madang, a coastal province in the north of Papua New Guinea (PNG) and in the population of Kar Kar, an island situated near Madang. Of the population tested, 97% from Madang and 89% of that from Kar Kar Island were either .alpha.+-thalassemia heterozygotes or homozygotes. No examples of the deletion form were detected in the Eastern Highlands of PNG. The haplotype frequencies of .alpha.+-thalassemia (-.alpha./) in Madang and Kar Kar Island were found to be 81.33% and 66.67%, respectively. A more detailed analysis of the gene deletion revealed that in both populations 96% were of the 4.2 kilobase (kb) type and 4% were of the 3.7-kb type. This group is the only example in which the 4.2-kb deletion is predominant over 3.7-kb defect. The presence in high frequencies of .alpha.+-thalassemia in the coastal area of Madang and on the neighboring island, where malaria was long holoendemic or hyperendemic, and its virtual absence from the nonmalarious highlands of PNG suggest the role of malaria as the selective factor in maintaining .alpha.+-thalassemia. If this selective pressure is still operating, and since .alpha.+-thalassemia has no apparent homozygous disadvantage, the abnormal haplotype (-.alpha./) will be in the process of fixation in this population.