The Evolution of Introns in Human Genes


Introns, which constitute the largest fraction of most eukaryotic genes and which had been considered to be neutral sequences, are increasingly acknowledged as functionally important parts of our genomes. For quite some time, research on levels of nucleotide substitution in human introns has been incomplete and yielded contradictory results, but the finishing of the chimpanzee genome allowed for new and more detailed studies that are proving to be key to unveil intronic functions.

Keywords: introns; substitution rates; human–chimpanzee divergence; gene regulation

Figure 1.

Mean divergence (Ki) of introns at different ordinal positions along the gene. Single introns are plotted separately and introns at ordinal position higher than 17 were pooled together.

Figure 2.

Mean divergence (Ki) of introns in different classes of length. Short introns (49–1029 nucleotides) were separated in classes of 50 nucleotides of increasing length and long introns (>1029 nucleotides) are pooled together in a single last class.

Figure 3.

Nucleotide substitution rates in introns and coding sequences. Intronic substitution rates (Ki) plotted against (a) synonymous substitution rates (Ks); (b) nonsynonymous substitution rates and (c) protein evolution rates (Ka/Ks).



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Further Reading

Rodriguez‐Trelles F, Tarrio R and Ayala FJ (2006) Origin and evolution of spliceosomal introns. Annual Review of Genetics 40: 47–76.

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Gazave, Elodie, Fernando, Olga, and Navarro, Arcadi(Apr 2008) The Evolution of Introns in Human Genes. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0020854]