PTC-tasting ability in populations living in Kirghizia with special reference to hypersensitivity: its relation to sex and age.

The dimorphism in sensitivity to PTC, with a dilution scale up to 29, was studied in 320 male and 320 female Kirghiz students, 45 male and 200 female Russian students in Frunze, and in 734 Kirghiz schoolchildren in a high-altitude area of South Kirghizia. Gene t frequency was 0.44 for the Kirghiz students, 0.56 for the Russian students, and 0.54 for the Kirghiz schoolchildren. In all the groups studied it was established that such factors as sex and age have no modifying effect on sensitivity to PTC and the pattern of the distribution of sensitivity. In all the groups the frequency of 'tasters' exceeded that of 'nontasters.' Among the Kirghiz students there was a very small percentage (1.2%) of hypersensitive subjects (dil. No. 18), while 14.1% of the Kirghiz children of one Kyzyl-Dzhar school were hypersensitive. Genealogical studies showed that all the hypersensitive subjects belonged to one small stock and lived in the same village. Family studies of probands suggest the existence of a new (third) allele (T2) which determines hypersensitivity to PTC.