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Nature Reviews Genetics 5, 773–782 (1 October 2004) | doi:10.1038/nrg1451

How did alternative splicing evolve?

Gil Ast

Alternative splicing creates transcriptome diversification, possibly leading to speciation. A large fraction of the protein-coding genes of multicellular organisms are alternatively spliced, although no regulated splicing has been detected in unicellular eukaryotes such as yeasts. A comparative analysis of unicellular and multicellular eukaryotic 5|[prime]| splice sites has revealed important differences — the plasticity of the 5|[prime]| splice sites of multicellular eukaryotes means that these sites can be used in both constitutive and alternative splicing, and for the regulation of the inclusion/skipping ratio in alternative splicing. So, alternative splicing might have originated as a result of relaxation of the 5|[prime]| splice site recognition in organisms that originally could support only constitutive splicing.