Genetics Essay

948 WordsApr 20, 20154 Pages
Tasting Phenylthiocarbamide (PTC) –Restriction Fragment Length Polymorphism (RFLP) Analysis of student Phenotypes and Genotypes at the PTC Gene. There exist many individual differences in terms of how one perceives his environment, for example, in sensing various chemicals. Studies in the past have shown that polymorphisms in human sensory receptor genes could alter perception by coding for functionally distinct receptor types (Bufe et al., 2005). In relation to this, phenylthiocarbamide (PTC) or phenylthiourea is an organic compound known to have the unusual property of tasting very bitter to some people whereas being virtually tasteless to the other. The ability to taste PTC primarily depends on the genetic makeup of the taster. It is controlled by the TASR238 taste receptor gene, also known as PTC gene, which is located on the long arm of chromosome 7 (7q34) and is about 1003 base pairs in length. It has been reported that sequence variants (polymorphism) in this gene correlate with differences in bitterness recognition of PTC. The three most common occurrences of polymorphisms in TAS2R38 are at amino acid position 49, where either a proline or an alanine is encoded, at position 262, where either an alanine or a valine is encoded, and at position 296, where either a valine or an isoleucine is encoded. The two commonly found haplotypes are PAV and AVI, whereas the haplotypes AAI, PVI, and AAV do not occur frequently. Therefore, there are two alleles that are mostly found coding for amino acid with haplotypes PAV and AVI (Bufe et al., 2005). The variation in the ability to taste PTC appears to be widely studied as a Mendelian trait. In the past, many surveys regarding the genetics of taste thresholds were performed to classify the tasters and non tasters of PTC roughly according to their taste acuity by means of dilutions at which the bitter taste was first

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