If one (or more) Tas2rs underlie the chromosome 6 QHCl taste sensitivity QTL, we would predict that one (or more) Tas2r genes would exhibit one of three likely characteristics: (1) A Tas2r allele is a pseudogene, or is deleted, in D2 (QHCL-insensitive), but not B6 (QHCl-sensitive), mice; (2) Missense mutations in the single coding exon of a D2 Tas2r allele impact protein functions such as ligand binding or receptor coupling to downstream signaling cascades; (3) Mutations in noncoding or regulatory regions of a D2 Tas2r allele affects expression of the protein product.