Several studies have shown multigenic inheritance of sweetener preferences.[107,110,111,123,124] Consistent with these findings, several lines of evidence indicate that allelic variation of the mouse Tas1r3 locus does not account for all the genetically determined differences in sweetener preferences. Analysis of multiple inbred mouse strains has shown that the Tas1r3 genotype explains only 78% of genetic variation in saccharin preference.[113] In the B6 × 129 F2 cross, the Tas1r3 genotype explained 64–96% of genetic variation in preference scores for different sweeteners, but only 10–35% of genetic variation in sweetener intakes.[126,130] Responses to sweeteners in brief-access tests differ among mouse strains but do not seem to be associated with Tas1r3 alleles.[115] Thus, a substantial part of the genetic variation in taste responses to sweeteners among mouse strains is attributed to loci other than Tas1r3. Taste responses to glycine provide a remarkable example: although mouse strains differ in responses to glycine,[110,132] this variation is not attributed to the Tas1r3 genotypes.[116,130]
