Intermediate sucrose octa-acetate sensitivity suggests a third allele at mouse bitter taste locus Soa and Soa-Rua identity

Mice have been characterized as either tasters or non-tasters of the bitter compound sucrose octa-acetate(SOA). However, 11 of 17 supposedly non-taster inbred strains were found to avoid 1 mM SOA. All 17 strains were indifferent to 0.1 mM SOA. Taster strains avoided both concentrations. The intermediate phenotype was dubbed demitaster. A consistent phenotypic dominance order was found in crosses among both inbred and outbred strains (taster > non-taster > demitaster). Demitasters were found (with tasters) in an outbred strain showing monogenic segregation for SOA avoidance. This, plus monogenic segregation in a back-cross of taster to demitaster inbred strains, suggested a third allele at the Soa locus (Soac). Demitaster allelism was supported by the strong associations found in 15 strains between the three SOA phenotypes and HindIII restriction fragment patterns for the closely linked Prp (proline rich protein) loci. SOA demitaster strains were also intermediate in raffinose undeca-acetate (RUA) avoidance. Furthermore, B6.SW-Soa2 congenic mice avoided not only SOA, but RUA and eight other acetylated sugars. A previously proposed separate RUA-sensitivity gene (Rua) thus appeared to be redundant.