Exercise: Using Primer-BLAST - Designing specific primers for a SNP in the human PTC receptor site (30 min)Teresa Strecker

Directions

Mammals can detect only five basic tastes: sweet, sour, bitter, salty, and umami (the tast of monosodium glutamate). The ability to distinguish these tastes is due to specific taste receptors on the surface of the tongue’s taste cells. One such taste receptor for bitterness is encoded by the PTC taste receptor gene, TAS2R38. Phenythiocarbamide (PTC), also known as phenylthiourea (PTU), does not occur in food, but related chemicals do, and food choice is related to a person's ability to taste PTC.

About 70% of people can taste PTC and the ability to taste PTC is considered a dominant genetic trait. 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. The test to determine PTC sensitivity is one of the most commonly used genetic tests on humans at this time.

To learn more about the bitter tasting differences among individuals watch this short video:

As you saw in this video, one way to determine if a person is a strong bitter taster (super taster) is to have them taste paper that has been treated with PTC (Phenythiocarbamide).  The reason there are differences between individuals with regard their ability to taste PTC is due to SNP (single nucleotide polymorphisms) in the gene that encodes the bitter tasting receptor, TAS3R38.

There are three SNPs (single nucleotide polymorphisms) along the TAS2R38 gene that may render its protein unresponsive to PTC. Any person with a single functional copy of this gene can make the receptor 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.

In this exercise you will design PCR primers to isolate SNPs found in the TAS2R38 gene.