Fig. 3.

Average daily saccharin solution consumption by segregating 129.B6-Sac partially congenic (N₄) mice in 96-h two-bottle tests (Means ± Standard Errors). Haplotypes of three congenic substrains are shown at the bottom of the figure. Each substrain carries a B6 donor chromosome fragment of different length, with recombinations between D4Mit254 and D4Mit209, D4Mit209 and D4Mit256, or between D4Mit256 and D18346. The partially congenic mice with one copy of the Sac-containing chromosome fragment from the B6 strain (n = 81, filled bar) had higher saccharin intakes than did the mice homozygous for the 129 Sac allele [n = 97, open bar; F(1,166) = 75.5, p < 0.00001, 3-way ANOVA]. The saccharin intakes by the Sac-heterozygous (B6/129) and homozygous (129/129) mice from each of the three substrains were respectively 12.6 ± 0.7 (n = 39) and 7.3 ± 0.2 (n = 62) ml/30 g BW (the substrain with the shortest donor fragment); 11.7 ± 0.9 (n = 26) and 7.9 ± 0.5 (n = 24) ml/30 g BW (the substrain with the intermediate donor fragment); and 10.7 ± 0.7 (n = 16) and 6.6 ± 0.4 (n = 11) ml/30 g BW (the substrain with the longest donor fragment). The differences among the substrains were non-significant [F(2,166) = 2.0, p = 0.14]. Females had higher intakes than did males [F(1,166) = 9.6, p = 0.002], but the effect of genotype was similar within each gender [gender × genotype interaction, F(1,166) = 0.4, p = 0.54]. Analysis of preference scores showed similar results (not shown). Because the overlapping part of the donor chromosome fragments in the three substrains ends proximally between D4Mit256 and D18346, Sac must be located distal to D4Mit256. Because neither 129.B6-Sac substrain carries the B6 allele of Gpr70, it is located outside of the Sac-containing donor fragment and proximally to D4Mit209 (the marker included in the largest donor fragment).