Correlation between phenylthiocarbamide taster status and quinine sensitivity
Each person has unique preferences for certain tastes and types of food. Some of these preferences are due to environmental factors, while others have genetic components (Yeomans 2010). One such genetically influenced trait is the ability to taste phenylthiocarbamide (PTC). PTC was discovered by accident in 1931 by colleagues Arthur Fox and C. R. Noller. While working in the laboratory, dust from the PTC bottle flew around and Noller complained of the bitter taste while Fox noticed nothing. The two then tried the crystals and observed a distinct difference in their ability to taste PTC. Fox proceeded to investigate this phenomenon and determined that he found both tasters and non-tasters within varied groups of individuals (Fox 1932). PTC has since been a topic of wide interest within fields as diverse as genetics, psychophysiology, ecology, evolution, nutrition, and science education (Wooding 2006). Due to the fact that the phenotype is nearly impossible to guess until explicitly tested, yet once tested quite striking, it has often been used to spice up educational lessons (Wooding 2006).
Aside from the pedagogical implications of such a striking phenotype, many pioneering studies relating to PTC and the taster/non-taster phenotype have been conducted since its discovery (Wooding 2006). Directly after Fox presented his findings for the National Academy of Sciences, Blakeslee also presented his large-scale study of PTC inheritance within families and saw a similar phenomenon of taster and non-taster phenotypes. Furthermore, Blakeslee classified the tasters according to their taste acuity using dilutions at which the bitter taste was first detected (Blakeslee 1932). Although another researcher had determined that the non-taster status was conferred by a recessive allele at a single locus due to the apparent offspring ratios resulting from specific parental crosses (Synder 1931), Blakeslee agreed but also concluded that the relationship was not that simple once the detection threshold and strength of the sensory reaction was considered (Blakeslee 1932).
Since the initial investigations regarding the inheritance of the PTC gene, much more research has been done over the ensuing 81 years including the identification of the gene responsible for PTC sensitivity (Kim 2003). This study identified a region on chromosome 7q that contained a number of TAS2R bitter taste receptor genes (Kim 2003). Within this region, three coding SNPs give rise to five haplotypes that were identified with the most common being the non-taster AVI haplotype and the taster PAV haplotype, which account for approximately 98% of the haplotypes (Kim 2003). Similar to previous studies (Blakeslee 1932, Chang 2006), Kim et al. accounted for the variation in sensitivity to PTC and were able to find a genetic correlation; PAV homozygotes had the highest mean PTC scores,...