Bitter Taste Receptors (BTRs) is one of the five basic taste receptors that mammals have: Sweet, sour, bitter, salty, and umamu (monosodium glutamate, or MSG. Means "good tasting" in Japanese). Gustatory cells are found inside each taste bud, and at the end of those cells are taste receptors. The taste receptors only bind to a specific molecule, which, when bonded, sends a signal directly to the brain. ~

BTR was fist discovered on accident, when, in the 1930s, Arthur Fox synthesized phenylthiocarbamide (PTC). The PTC was able to escape into the air, where lab-mate C.R. Noller mentioned that the air tasted bitter. Fox had not noticed it, even after tasting the crystals of PTC. Soon after Fox started asking his family and friends, who also said varying results.

Today, after some research, we know that bitter taste is inherited dominantly. Specifically, the ability to taste PTC is based on one gene TAS2R38 discovered in 2003. It is thought the reason for why we have PTC receptor is for discerning if plants that we (used to) eat is poisonous or not.

Gene Isolation

Using DNA isolation, you can predict if you have the gene for tasting PTC. Here is me finding out my TAS2R38 gene.

First, I isolated my DNA, which is probably the hardest part of this. I messed up my first time of isolation, but redid it.

After isolation, I setup a PCR reaction that Specifically targets a part of the TAS2R38 gene that contains an allele for it. The PCR product is 221 base pairs (bp).

Now having PCR product amplified, how do we determine one allele to another. Using restriction enzymes! In this reaction, HaeIII is used as it cuts bluntly on GGCC sequence: GG^▼CC
CC_▲GG If you are a non-taster, the sequence will be GGGC, which HaeIII won't cut.

Using a 2% agrose gel with electrophoresis, if you are a taster, there would be two bands (177bp and 44bp, cut), and a non-taster will have one band (221bp, uncut).