Examination of the Tas2R38 Gene and Its Specific Nucleotide Differentiations to Determine Ability to Taste Phenylthiocarbamide

2113 Words Sep 16th, 2014 9 Pages

INTRODUCTION Although humans are essentially genetically identical as a whole, there are some minute variances in our gene coding that allow for differences in our interactions with the world. These genetic modifications may have extensive detrimental effects, small effects, or no apparent effect at all. A few of these alterations can even affect our senses. In this lab, we examine how a discovery by a scientist gives us insight into how a relative dissimilarity between humans can affect the ability or inability to taste certain chemicals. Scientist Arthur Fox learned that the chemical phenylthiocarbamide,
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One restriction endonuclease, called HaeIII, reads and cuts the DNA depending upon what nucleotide sequence is present at location 145 in the amplified 220 bp TAS2R38 gene region. Once the desired nucleotide sequence is recognized at this position (GGCG), this enzyme will clip the DNA at that region since there is a restriction site present at this allele, and will not clip if the DNA sequence is read as GGGG since there is no restriction site for “G” allele for HaeIII. This means that the PTC nontasting allele is recessive (t) and the PTC tasting allele is dominant (T). These slices of DNA fragments can be further examined by agarose gel electrophoresis which allows base pairs to be divided while using an electric current. Marker DNA is also useful, as it is used to approximate the size of the DNA fragments that have migrated through the agarose.
Since PTC tasting is a dominant trait (TT or Tt), certain techniques in the lab were used to figure out which alleles we possessed. We hypothesized that those students whose DNA bands were less than 220 bp had the “TT” or “Tt” genotype, and those whose bands were not cut had the “tt” genotype. We also hypothesized that those with the “tt” genotype would not be able to taste PTC (non-taster phenotype), while those with the “Tt” genotype would be mild tasters and those with the “TT” genotype would be strong tasters (tasting phenotype). In order to find out which alleles we

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