Figure 2.

Exon-form extension rules. Exon forms are shown as filled boxes; splices are shown as angled lines; exon observations (exon_obs) from individual ESTs are shown as horizontal lines; the 5′- and 3′-ends of ESTs are shown as vertical lines. (A) An exon_obs is consistent with an exon form if it matches exactly at both ends of the exon form, or its only mismatch is that the EST ends within the exon_form. (B) An exon form with no splice site on one side can be extended on that side by exon_obs that extend the alignment interval. (C) An exon form with defined splice sites cannot explain exon_obs with different splice sites; new exon forms must be created to explain these exon_obs.