Why do genes have introns? Recombination might add a new piece to the puzzle

doi:10.1016/S0168-9525(01)02236-3

Trends in Genetics

Volume 17, Issue 4, 1 April 2001, Pages 172-175

https://doi.org/10.1016/S0168-9525(01)02236-3 Get rights and content

Abstract

Much progress has been made recently regarding when and how spliceosomal introns invaded eukaryotic genomes. Although the ‘intron early–intron late’ debate seems to be settled, the original and essential question remains: why have introns at all – do they have a purpose? Analyses of the relationship between intron length and recombination in Drosophila shed new light on the forces that drive the evolution of introns. Comeron and Kreitman proposed recently that introns are advantageous because they enhance within-gene recombination and therefore increase selection efficacy (Hill–Robertson effects). However, their observations can also be explained by alternative neutralist models.

Section snippets

The evolution of introns

Thanks to the data generated by genome projects, large-scale inter- and intra-genomic comparative analyses are now feasible. Because the cost incurred by an intron is expected to be proportional to its size, the analysis of the factors that affect intron size should help to understand whether their evolution is governed by selection and, if so, how. Notably, population genetics models predict that, all else being equal, the efficacy of natural selection is decreased in regions of low

Conclusion

In conclusion, the present data do not allow the teasing apart of the selectionist and neutralist models for the evolution of intron size in Drosophila. It is possible that variations of intron length within and between genomes essentially reflect differences in the dynamic equilibrium between rare TE insertions and frequent, but short, base deletions rather than variations in selective pressure. Although it remains speculative, the model of Comeron and Kreitman is attractive. It is generally

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Trends in Genetics

Abstract

Section snippets

The evolution of introns

Conclusion

References (22)

The recent origin of spliceosomal introns revisited

Curr. Opin. Genet. Dev.

Intron phylogeny: a new hypothesis

Trends Genet.

Alternative splicing of human genes: more the rule than the exception?

Trends Genet.