Figure 4.

col-182 modifies the effects of natural genetic variation on worm movement and shape. Genome-wide statistics are shown for two bivariate response models of col-182 indel $\times$ SNP genotype, worm length/width (A) and Rol/Sqt sparse discriminant functions (B), using diallelic SNPs segregating in 363 recombinant inbred lines of the C. elegans multiparent experimental evolution (CeMEE) panel. Statistics are from a likelihood ratio test for a full additive and interaction linear model against a null model of no genetic effects. Permutation thresholds for genome-wide significance (FDR = 0.2) are shown in red, light shaded regions show 1.5 LOD drop QTL intervals (expanded to a minimum of 300 Kb for visibility), and the location of col-182 on the X chromosome is indicated by a dark gray line. Effect plots at right show genotype class means and standard errors for QTL with significant interactions (parametric bootstrap against additive models, $\alpha =0.05$ ). Trait values shown are the first principal component for length/width, and the Sqt discriminant function, which explains most of the interaction in the Rol/Sqt bivariate model. Reference-based genotype is on the x-axis. Genotype and phenotype data in File S15, code in File S16.