Splicing signals and modes of alternative splicing.
Top: Conserved motifs at the exon/intron boundaries are shown. The size of the nucleotide at a certain position is proportional its frequency. Nucleotides that contribute to the consensus motive are shown in yellow, the branch point in orange. Bottom: five common modes of alternative splicing, with different paths indicated in green and red. Multiple modes can apply in combination to the same transcripts, and additional isoforms can be generated by alternative usage of promoters and PolyA sites.