Univariate and bivariate single-point QTL analyses for the traits gene expression levels of the genes GRK6 and TCOF1 along chromosome 5. Gene expression levels of the genes TCOF1 and GRK6 are linked to the same SNPs. *, joint single-point QTL analysis. The distance along chromosome 5 in megabase pairs (Mb) is on the horizontal axis. LOD scores of QTL analyses are on the vertical axis.