Fig. 1. Histograms of maximum ORF lengths. (A) Black bars are plots of the lengths of the longest ORFs represented in 120 segments (average length=800 nucleotides) of sea urchin 3'-UTRs. The segments were obtained from all sea urchin genes in GenBank as of 7/11/2000 for which 3'-UTR sequences >600 nucleotides were available (39 genes). Most of the ORFs are short and none was >350 nucleotides in length. White bars are of the lengths of the longest ORFs in a random sample of 120 ESTs (average length=794 nucleotides) that yielded strong BLAST matches (P<10^-7). There is little overlap between this distribution and the one derived from 3'-UTR sequences. (B) Plot of maximum ORF lengths in 120 randomly selected ESTs from the ‘no match’ category (average length=796 nucleotides). Because the cDNA library was directionally cloned, only the longest ORFs in the three positive reading frames (+1, +2, +3) were considered. 20/120 clones (16.7%) contained an ORF equal to or longer than 350 nucleotides.