Figure 2

Variance of expression logratios of 2127 genes (SET 1) and 8954 genes (SET 2) within different perturbations and tissue types. For perturbations, logratios were calculated as experimental versus control samples, whereas for tissues they were calculated as the expression in a given tissue type relative to the average vector of all 56 or 55 tissue types, respectively. The variance of expression was sorted in decreasing order for SET 1 (left plot) and for SET 2 (right plot), for both perturbations and tissue types, and plotted against their percent ranking. Variances originating from tissue affiliation were signifcantly higher than variances arising from perturbations, except for a variety of cancers and drugs (see also Additional file 3).