Absolute number of identified transcription start sites in correlation to the length of their 5′-untranslated regions (5′-UTRs). The 1,642 TSSs located upstream or in coding direction of known CDSs were used to determine the length of the 5′-UTRs for each CDS. The 5′-UTR length was calculated as the distance between an identified TSS to the next TLS. The absolute number of TSSs is grouped in 5 bp intervals of 5′-UTR lengths (1–5, 6–10, 11–15 etc.), whereas the most distant right bar represents all 5′-UTRs longer than 500 bases.