Figure 1.

Common Alternative splicing events. The mechanisms of the most common alternative splicing events: Exon Skipping, Intron Retention, Alternative 5′ splice site selection, and Alternative 3′ Splice Site selection, are presented. There are several other alternative splicing events that are not shown here. The colored bars (blue, orange, and green) represent exons, while the black lines connecting them represent intronic segments. Exon skipping—The most prevalent mechanism in vertebrates and invertebrates where specific exons in the pre-mRNA are skipped in the mature mRNA transcript. Intron retention—Common in lower metazoans and plants, it is a process where an intron is retained in the mature mRNA, and Alternative 3′/5′ acceptor/donor sites—A process that involves exons that are flanked by competing splice sites on one end (3′/5′) and a fixed splice site on the opposite end, resulting in an alternative region that is either included or excluded in the mature mRNA.