Figure 6.

The effect of 5'-proximal coding intron presence on gene expression. (a) Smoothed histogram of the mean expression level with respect to presence/absence of 5'-proximal coding region introns (5PCIs). A kernel density estimator was fitted to the expression data and the corresponding probability density is plotted as a function of the mean expression level. The black line corresponds to the probability density for transcripts without any 5'UTR introns or any 5PCIs. The red line represents the probability density for 5'UTR intronless transcripts that have 5PCIs. The vertical line represents the top 5% of mean expression level of all genes without 5'UTR introns.