To study the non-Tas1r genes involved in sweet taste, we began selective breeding of mouse lines divergent in sweetener consumption. To eliminate the Tas1r3 effects, we crossed B6 inbred mice with 129.B6–Tas1r3 congenic mice. As a result, all mice in this cross had only the B6 Tas1r3 allele. Despite genetic identity at the Tas1r3 locus, mice from the F2 generation varied widely in consumption of 20 mm saccharin and 30 mm glycine, but there was no correlation between these two traits. We therefore began selective breeding of mouse lines with high and low saccharin intakes, and with high and low glycine preferences.[55,137] The large divergence between the selected strains demonstrates that much of genetic variation in mouse sweet taste responses depends on genes other than Tas1r3. To map these genes, we genotyped mice from the selected strains and found linkages on four chromosomes in mice selected for glycine preference, and linkages on five chromosomes for mice selected for saccharin intake. We have found the complex genetic architecture of sweetener preferences, with each progenitor strain contributing loci increasing or decreasing a
