TAS2R38 (taste receptor, type 2, member 38)

TAS2R38 is a bitter taste receptor, and its gene is responsible for PTC (phenylthiocarbamide) tastor polymorphism with three nonsynonymous substitutions at amino acid sites 49 (encoding proline or alanine), 262 (alanine or valine) and 296 (valine or isoleucine).  One Neanderthal individual was shown to be heterozygous for two major TAS2R38 alleles (proline-alanine-valine and alanine-valine-isoleucine), suggesting that the PTC polymorphism goes back to the common ancestor of modern humans and Neanderthals.  Balancing selection was proposed to explain this polymorphism, but it is not clear if any selection pressure really exists.