(A) Animals were genotyped at an average 1.5 cM density using 1,032 SNPs polymorphic between the parental strains. LOD scores computed using sex as an additive covariate (black) failed to detect significant linkage. A genome scan accounting for interactions between sex and QTL (red) showed evidence for suggestive linkage on Chromosome 1 and significant linkage on Chromosomes 3, 5, 11, and 19. Dashed and solid lines are thresholds for suggestive (p < 1 × 10−3) and significant linkage (p < 5 × 10−5), respectively.