Some scientists call the non-coding regions of the genome 'junk' DNA. But a paper appearing in the 20 Oct 05 issue of Nature (Vol. 437, No. 7062, pp. 1149-1152) provides evidence that these regions are actually under strong selection.
Using a recently developed population genetic approach, Peter Andolfatto shows that non-coding DNA in the fly Drosophila melanogaster is evolving more slowly than similar sites in coding DNA, due to pressure on the non-coding DNA to remain the same over time. Many previous studies of evolutionary rates examined changes in coding DNA without looking at non-coding DNA. The non-coding portions also exhibit an unusually large amount of genetic divergence between different fly species. The data from this study suggest that these regions are subject to adaptive evolution and purifying selection. On the basis of this analysis, Andolfatto proposes that the non-translated regions serve an important biological function.
"In Drosophila, the relatively junk-free regions between genes, which probably regulate gene expression, appear to be a major target of positive selection," writes Alexey S. Kondrashov in a related News and Views article.
Peter Andolfatto (University of California San Diego, La Jolla, CA, USA)
Alexey S. Kondrashov (National Center for Biotechnology Information, NIH, Bethesda, MD, USA)
(C) Nature press release.
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