Further Evidence for a Silent Allele and a Rare Variant in the ADA System

Abstract

Genetic polymorphism of human erythrocyte adenosine deaminase (ADA, EC.3.5.4.4) was discovered by Spencer et al. (1968) using starch gel electrophoresis. Three common phenotypes, designated ADA 1, 2−1 and 2 were due to two autosomal codominant alleles ADA*1 and ADA*2. Several rare electrophoretic variants, ADA 3(Hopkinson et al. 1969), ADA 4 (Dissing and Knudsen 1969), ADA 5 (Detter et al. 1970; Renninger and Bimboese 1970), ADA 6 (Radam et al. 1974), ADA 7 (Berg et al. 1975), ADA 8 (Jenkins et al. 1976), and ADA 9 (Nenkov et al. 1981; Henke et al. 1986) were subsequently found by family and population studies. There is also evidence for the existence of a silent allele (Giblett et al. 1972; Brinkmann et al. 1973). Deficiency of ADA with very low or no activity in red and white cells is associated with severe combined immune deficiency disease (Giblett et al. 1972; Dissing and Knudsen 1972; Chen et al. 1974). A point mutation in the ADA sequence appears to be responsible for the loss of function in this allele (Bonthron et al. 1985). Heterozygotes for ADA*Q0 are aoparently healthy. The ADA locus has been assigned to the long arm of chromosome 20 (Tischfield et al. 1974; Mohandas et al. 1984).KeywordsXanthine OxidaseAdenosine DeaminasePurine Nucleoside PhosphorylaseCommon PhenotypeSilent AlleleThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.