In mammals, sweetness perception is initiated when sweeteners interact with taste receptor proteins from the T1R family expressed in taste receptor cells in taste buds of the oral cavity. Thus, sweeteners function as ligands of the G protein coupled T1R receptors. The mammalian T1R gene family consists of three genes named ‘taste receptor, type 1, member 1, 2 or 3’. Corresponding gene symbols abbreviate these names to TAS1R1, TAS1R2 or TAS1R3 (in humans) or Tas1r1, Tas1r2 or Tas1r3 (in rodents and other non-human animals). Corresponding protein symbols are T1R1, T1R2 and T1R3. Species origin of a protein can be indicated as hT1R1 (human T1R1) or mT1R1 (mouse T1R1). For brevity, when we refer to both human (TAS1R) and non-human (Tas1r) genes, we describe them as T1R genes. The three mouse Tas1r genes are located in the distal chromosome 4 in the order: Tas1r2 – Tas1r1 – Tas1r3. Their human orthologues reside in a region of conserved synteny in the short arm of human chromosome 1 (1p36) in the same order: TAS1R2 – TAS1R1 – TAS1R3. The mouse Tas1r genes contain
