Mutually exclusive exons in genes of the Drosophila melanogaster X chromosome. The figure illustrates how many of the mutually exclusive exons, which were annotated based on Flybase transcripts, share the following features: high sequence similarity, similar length, same reading frame, and a minimal exon length (15 residues). The blue slice indicates exons characterised by these features and found by the new algorithm. The red slice indicates exons not sharing these features. At the bottom, the figure shows the exon-intron structure of the Phosphorylase kinase γ gene, which includes the only cluster of mutually exclusive exons that was not found by the new algorithm.