Figure 1.

Distribution of gene expression levels. (A) Kernel density estimates of RPKM distributions of RNA-seq data within exons, introns and intergenic regions as indicated. The fragments used to estimate intron and intergenic RPKM were based on randomizations using the same length distribution as the exonic parts of genes. The 90% quantile of the intergenic distribution is indicated. (B) Kernel density estimate of expression level distribution of microarray data (Wei et al, 2009). (C) Expectation-maximization-based curve fitting of RNA-seq data of A.