Abstract
Tandem exon duplications play an important role in the evolution of eukaryotic genes, providing a generic mechanism for adaptive regulation of protein function. In recent studies, tandem exon duplications have been linked to mutually exclusive exon choice, a pattern of alternative splicing in which one and only one exon from a group of tandemly arranged exons is included in the mature transcript. Here, we revisit the problem of identifying tandem exon duplications in eukaryotic genomes using bioinformatic methods and show that tandemly duplicated exons are abundant not only in the coding parts, but also in the untranslated regions. We present a number of remarkable examples of tandem exon duplications, identify unannotated duplicated exons, and provide statistical support for their expression using large panels of RNA-seq experiments.