Figure 1.

Relationship between gene compactness traits and expression levels. (A–D) Human genes are divided into eight bins according to their mean expression levels. Expression levels increase with the X-axis. The relationships between expression levels and (A) lengths of 5′-UTRs, (B) lengths of 3′-UTRs, (C) exon size and (D) lengths of introns are shown. In the lower panel, the relationships between expression levels of mouse genes and (E) lengths of 5′-UTRs, (F) lengths of 3′-UTRs, (G) exon size and (H) lengths of introns are shown.