Fruitfly genome is not junk Evolutionary biology

• Published in: Nature (London) Vol. 437; no. 7062; p. 1106
• Main Author: Kondrashov, Alexey S.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 20.10.2005
• Subjects: Humanities and Social Sciences; multidisciplinary; news-and-views; Science; Science (multidisciplinary)
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/4371106a

A comparison of two fruitfly genomes shows that much of their non-coding DNA is controlled by either negative or positive selection, dealing a double blow to the neutral theory of molecular evolution. The sound of silent DNA Time to junk the term ‘junk DNA’, or to reserve it for DNA of proven uselessness. Geneticists favour the less judgmental term ‘non-coding DNA’ for those parts of the genome not translated into protein, and there is growing evidence that it is important in disease, development and evolution. Despite this, little is known about the evolutionary forces acting on it. Now a new population genetics approach shows that most non-coding DNA in Drosophila melanogaster is subject to adaptive evolution and selection. The big surprise comes from a comparison between Drosophila species: a significant fraction of the divergence between species in non-coding DNA is adaptive, driven by positive selection. In fact, the number of beneficial substitutions in non-coding DNA is an order of magnitude larger than in proteins. Non-coding DNA includes ‘ cis -acting’ regulatory sequences, so this finding may reflect the immense importance of regulatory evolution, previously suggested on intuitive grounds.