ABSTRACT
Phenylthiocarbamide (PTC) is a chemical compound that tastes bitter to some people but not to others. Individual differences in recognition threshold are partially determined by alleles at a putative bitter receptor gene on chromosome 7 (TAS2R38), but it is not known to what extent these alleles determine sensitivity to bitter compounds within the same chemical class or to other taste qualities. Since propylthiouracil (PROP) has replaced PTC as a taste stimulus in recent studies, it is important to test the relationship between alleles of this gene and PROP sensitivity. Because the density of fungiform papillae on the tongue predicts perceived taste intensity, this trait may partially account for higher than average perceived intensity for these bitter compounds of some individuals and may interact with genotypes at the putative bitter receptor TAS2R38. Although alleles of the gene on chromosome 7 are related to PTC sensitivity, several lines of evidence suggest that other major genes influence the PTC trait as well as sensitivity to PROP and other compounds in this chemical family. There-fore, identification of genetic loci that modify this trait will contribute to our understanding of individual differences. Since bitter insensitivity is a 4 common trait that is perhaps related to food intake and thyroid metabolism, it may have serious consequences for human health.
