One of the genetic loci affecting sweet taste responses is dpa (d-phenylalanine aversion), which affects ability of mice to generalize conditioned taste aversion between d-phenylalanine and sucrose, inferring that dpa affects ability to detect the sweetness of d-phenylalanine. The dpa locus also affects responses of sucrose-sensitive fibres of the chorda tympani nerve to d-phenylalanine. The dpa locus was mapped to proximal chromosome 4, a region distinct from the subtelomeric chromosome 4 harboring the Tas1r genes.[133-136] It was suggested that the dpa locus can also affect responses to sweeteners in two-bottle tests.[111] Consistent with this, a locus on proximal chromosome 4, in the dpa region, was found to be suggestively linked to consumption of, and chorda tympani responses to, sucrose.[126] An epistatic interaction between effects on sucrose intake of this locus and the Tas1r3 locus suggests that these two loci may encode interacting components of sweet taste transduction.[126]
