Phenylthiocarbamide

Phenylthiocarbamide (PTC), also known as phenylthiourea, is an organic compound with the formula C_6H_5NHC(S)NH_2. This white crystalline substance is notable for its genetic basis for tasting ability, leading to its use in genetic and psychological research. The ability to taste PTC varies greatly among individuals and is a classic example of a simple genetic polymorphism within human populations.

Chemical Properties

Phenylthiocarbamide is characterized by its bitter taste, which can only be detected by some individuals. This variability is due to a difference in the TAS2R38 gene, which codes for a taste receptor on the tongue. The compound is soluble in water and ethanol, making it easy to administer in taste tests.

Genetics of PTC Tasting

The ability to taste PTC is determined by the presence of specific alleles of the TAS2R38 gene. Individuals with at least one copy of the dominant allele (usually denoted as "T") can taste PTC, while those with two recessive alleles ("t") cannot. This genetic trait follows Mendelian inheritance patterns.

Historical Context

The discovery of PTC tasting dates back to 1931 when Arthur Fox, a chemist, accidentally released a cloud of PTC powder. A colleague noticed the bitter taste, whereas Fox did not, leading to the discovery of taste variation. Subsequent research has explored the implications of this variation in taste perception, diet, and evolutionary biology.

Implications for Diet and Health

Research suggests that PTC tasting ability may influence food preferences and diet. For example, individuals sensitive to PTC may be more likely to find certain vegetables, like broccoli and Brussels sprouts, bitter and less palatable. This has implications for nutritional choices and health outcomes, as these vegetables are rich in beneficial phytonutrients.

Evolutionary Significance

The variation in PTC taste sensitivity is thought to have evolved as a defense mechanism against toxic plants. Bitterness often indicates the presence of toxins, so the ability to detect bitter compounds could have conferred a survival advantage to early humans.

Applications in Research

PTC tasting is used in genetic, psychological, and anthropological research as a model for studying human genetic variation, inheritance patterns, and the evolution of taste perception. It also serves as a tool for teaching genetics, illustrating the concept of dominant and recessive alleles.

See Also

• TAS2R38
• Taste receptor
• Genetic polymorphism
• Mendelian inheritance