Classification of exons as distinct and variant. A. Exon 2 of transcript 1 is selected as the distinct exon, because it is the longest of the three overlapping exons, 2, 5 and 6, at this genomic location. B. Exon 2 is classified as distinct because although both exons 2 and 6 occur twice (number of repeats = 2), exon 2 is longer. C. Exons 2 and 3 are made distinct because exon 5 includes both these exons as well as the intronic region separating them. Thus, exon 5 is classified as variant.
Chacko and Ranganathan BMC Genomics 2009 10(Suppl 1):S5 doi:10.1186/1471-2164-10-S1-S5