Supertasters have the TAS2R38 gene, a G protein-coupled receptor that allows us to taste glucosinolates, bitter-tasting compounds found in Brassica sp. plants. Phenylthiocarbamide (PTC) and 6-n-propylthiouracil (PROP) are ligands, chemicals that bond for this receptor and are used to test the genetic diversity of this gene in human populations.