Non-coding DNA adapts

Much of the "junk" DNA in Drosophila shows signs of either negative or positive selection, according to a study in this week's Nature. An analysis by Peter Andolfatto of the University of California, San Diego, reveals that around half of non-coding Drosophila DNA is evolutionarily constrained and that much of the remaining divergent DNA has undergone adaptive evolution. Both types of selection show that "this non-coding DNA actually has functional importance to the organism," said Andolfatto.

"We've known for a while that it was possible you'd see constraint—essentially, negative selection—on non-coding regions," said Gerald Wyckoff of the University of Missouri-Kansas City, who was not involved in the study, "but his methodology makes it so clear that this type of selection is abundant."

During the study, Andolfatto analyzed polymorphisms in 35 coding fragments and 153 non-coding fragments scattered across the Drosophila melanogaster X chromosome. He compared these data with D. melanogaster's ...