IES density is inversely proportional to gene expression level.

<p>Genes were binned according to their median expression level across 58 microarrays representing different cellular and growth conditions as described in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002984#pgen.1002984-Gout1" target="_blank">[38]</a>, <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002984#pgen.1002984-Arnaiz2" target="_blank">[39]</a>. The expression levels were divided into 30 bins as in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002984#pgen.1002984-Gout1" target="_blank">[38]</a>. The black points show the average IES density (per Kb) of genes in each bin. Linear regression was used to fit the points. Light gray bars show the distribution of genes according to their expression level (before binning).