Adenosine deaminase: racial distribution and report of a new phenotype.

Genetic variation of the enzyme, adenosine deaminase (ADA), can be detected by starch gel electrophoresis of human red cell lysates and an ap- propriate staining procedure (Spencer, Hopkinson, and Harris, 1968). Three phenotypes (ADA 1, ADA 2-1, and ADA 2) appear to be determined by two structural alleles, ADA' and ADA2. The fre- quency of the less common allele, ADA2, was re- ported to be 0 03 and 0 05 in London Negroes and Caucasians, respectively. Its frequency among Asiatic Indians was 0-12 (Hopkinson, Cook, and Harris, 1969). A very rare ADA 3-1 phenotype, found in an English family, has also been described (Hopkinson et al., 1969).