annotation of UTRs in those models in releases 3c and 7 (Fig. 6). Both the mean 5′ UTR and 3′ UTR length increase with each release between 3c and 7, with the mean 5′ UTR more than 41 bases longer in release 7 and the mean 3′ UTR 180 bases longer. Both increases are likely to be due to an increase in the amount of transcript data (ESTs and mRNAs) available to support the extension of transcripts.
