Figure 1.

Schematic of data and correlation calculation: $Y^{*}$ is a standardized expression phenotype matrix, $G^{*}$ is a standardized genotype matrix, and R is a correlation matrix. An entry in R (shaded dark gray) is obtained by summing the product of the entries of the corresponding row of $Y^{*\prime }$ and the corresponding column of $G^{*}$ (both shaded light gray). The matrix of LOD scores is an element-wise function of the correlation matrix.