Genetics of Sensory Thresholds: Taste for Phenyl Thio Carbamide

Abstract

Further evidence is given to show that inability to taste P. T. C. crystals is a Mendelian recessive. This tastp deficiency is only an apparent one, a matter of differences in thresholds. Data secured from 206 parents and their 227 children, when plotted for threshold values, assumes the form of a bimodal curve with the few "non-tasters" at one end. All the non-tasters of the crystals tested were able to taste the compound in saturated solutions in warm dilute alcohol. The factors responsible for the bimodality of the curve and the inability to taste crystals are unknown; however, the pH of the saliva is shown not to be the controlling factor. In regard to the primary tastes (salt, bitter, sweet, sour), some individuals are relatively poor tasters of all; others are relatively acute tasters of all. There was no close connection, however, between ability to taste the 3 bitter substances, P. T. C., quinine, and picric acid. Several individuals were unable to discriminate between bitter and sour; but called the substances in dilute solutions sour, and in concentrated solutions bitter.