Figure 1
Positional identification of the Sac (saccharin preference) locus. a. Linkage map of mouse distal Chr 4 based on data from the B6 × 129 F2 intercross. The X axis shows distances between markers in recombination units (cM). The Y axis shows the logarithm of the odds ratio (LOD) scores for sucrose and saccharin consumption. The LOD score peaks (indicated by black triangles) and confidence intervals (solid horizontal line for sucrose, 4.5 cM, and dotted horizontal line for saccharin, 5.3 cM) define the genomic region of the Sac locus. b. Average daily 17 mM saccharin consumption by mice from parental 129 and B6 strains (left), B6 × 129 F2 hybrids (center), and congenic 129.B6-Sac mice (right) in 96-hr two-bottle tests with water (means ± SE). Tas1r3 genotypes of the F2 and congenic mice and mouse numbers are indicated on the bars. Differences between parental strains and among the F2 and congenic genotypes were significant (p < 0.0001, ANOVA). F2 and congenic B6 homozygotes and heterozygotes for Tas1r3 did not differ from each other, and had higher saccharin intakes compared with 129 homozygotes (p < 0.0001, post hoc tests). c. Linkage map of the Sac-containing region defined based on the size of the donor fragment in the 129.B6-Sac congenic strain (black box). Distances between markers were estimated based on the B6 × 129 F2 intercross (see panel a). d. A contig of bacterial artificial chromosome (BAC) clones and physical map of the Sac region. BAC clones are represented by horizontal lines. Dots indicate marker content of the BAC clones. e. Genes within the Sac-containing interval. Filled areas indicate predicted genes. Arrows indicate the predicted direction of transcription. Figure reproduced with permission from [253].