Frequencies of pseudocholinesterase variants in Icelanders, Greeks and Pakistanis.

THE formation of the human pseudocholinesterase variants is controlled by at least four alleles at one autosomal locus termed E1 (ref. 1). The four alleles are , , and (refs. 2–5). The heterozygotes have been found in remarkably uniform frequencies, about 3 to 6 per cent, in Caucasians from Europe and North America3,8–11, and also in Australian aborigines12 and Mexican Indians13, but are relatively rare among Negroes11 and Mongoloids10,11,14.