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Infobox disclaimer and references
Phenylthiocarbamide (PTC), also known as phenylthiourea (PTU), is an organosulfur thiourea containing a phenyl ring.
It has the unusual property that it either tastes very bitter or is virtually tasteless, depending on the genetic makeup of the taster. The ability to taste PTC is a dominant genetic trait, and the test to determine PTC sensitivity is one of the most commonly used genetic tests on humans.
One study has found that non-smokers and those not habituated to coffee or tea have a statistically higher percentage of tasting PTC than the general population. PTC does not occur in food, but related chemicals do, and food choice is related to a person's ability to taste PTC. There is conflicting evidence as to whether a higher percentage of women than men can taste PTC.
The genetic taste phenomenon of PTC was discovered in 1931 when a DuPont chemist named Arthur Fox accidentally released a cloud of a fine crystalline PTC. A nearby colleague complained about the bitter taste, while Dr. Fox, who was closer and should have received a strong dose, tasted nothing. Fox then continued to test the taste buds of assorted family and friends, setting the groundwork for future genetic studies. The genetic correlation was so strong that it was used in paternity tests before the advent of DNA matching.
In 1976, a remarkable inverse relationship between taster status for PTC and for a bitter component of the fruit of the tree Antidesma bunius was discovered. Research on the implications still continues.
Some chimpanzees share the ability to taste PTC. However, chimpanzee PTC tasting relies on a different enzyme than human tasting, suggesting that the ability evolved independently in both species.
Role in taste
There is a large body of evidence linking the ability to taste thiourea compounds and dietary habits. Much of this work has focused on 6-propyl-2-thiouracil (PROP), a compound related to PTC that has lower toxicity. A supertaster has more of an ability to taste PTC. On the other hand, heavy cigarette smokers are more likely to have high PTC and PROP thresholds (i.e. are relatively insensitive).
Ability to taste PTC may be correlated with a dislike of plants in the Brassica genus, presumably due to chemical similarities.
There are three SNPs (single nucleotide polymorphisms) along the gene that may render its proteins unresponsive. There is conflicting evidence as to whether the inheritance of this trait is dominant or incomplete dominant. Any person with a single functional copy of this gene can make the protein and is sensitive to PTC. Some studies have shown that homozygous tasters experience a more intense bitterness than people that are heterozygous; other studies have indicated that another gene may determine taste sensitivity.
- (2001). Generating Transparent Zebrafish: A Refined Method to Improve Detection of Gene Expression During Embryonic Development. Marine Biotechnology 3 (6): 522–527.
- Question No. 19866. Science Centre Singapore. URL accessed on 5 December 2009.
- Fischer, R., Griffin, F. and Kaplan, A. R. (1963). Taste thresholds, cigarette smoking, and food dislikes. Medicina experimentalis. International journal of experimental medicine 9: 151–67.
- Kaplan AR, Glanville EV, Fischer R (1964). Taste thresholds for bitterness and cigarette smoking. Nature 202 (4939): 1366.
- Forrai G, Bánkövi G (1984). Taste perception for phenylthiourea and food choice—a Hungarian twin study. Acta Physiol Hung 64 (1): 33–40.
- Lee Phillips M. Scientists Find Bitter Taste Gene. URL accessed on 5 December 2009.
- Henkin, R.I. and W.T. Gillis (1977). Divergent taste responsiveness to fruit of the tree Antidesma bunius. Nature 265 (5594): 536–537.
- (2006). Independent evolution of bitter-taste sensitivity in humans and chimpanzees. Nature 440 (7086): 930–4.
- Kim UK, Jorgenson E, Coon H, Leppert M, Risch N, Drayna D (2003). Positional cloning of the human quantitative trait locus underlying taste sensitivity to phenylthiocarbamide. Science 299 (5610): 1221–1225.
- (2012). Genetic study of phenylthiocarbamide (PTC) taste perception among six human populations of Jammu and Kashmir (India). Egypt J Med Hum Genet 13 (2).
- Dennis Drayna's home page. Drayna has done extensive studies of PTC in various populations
- Population Study and Applications Using PTC Paper
- Classroom activity description using PTC paper
- OMIM 171200 Thiourea tasting
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