High incidence of the silent allele at cholinesterase locus I in Vysyas of Andhra Pradesh (S. India).

Four-hundred and ninety individuals belonging to the Vysya caste from Andhra Pradesh were screened for pseudocholinesterase variants at the E1 and E2 locus. A high incidence of the silent allele (gene frequency=0.1112) was recorded with homozygotes exceeding 2% of the population. Dibucaine- and fluoride-resistant alleles were found in a heterozygous form with the usual alleles in four individuals each. No C5+ variant at the E2 locus was found.