Genes, which code instructions for making an organism, constitute a small part of DNA.
Scientists used to think the rest of DNA was junk. But lately, they have discovered that such material is hardly garbage.
A new University of California San Diego study backs up those findings. It suggests that regions of non-coding DNA, long thought to serve no purpose, actually help maintain an organism's genetic makeup.
The report, led by assistant professor of biology Peter Andolfatto, appears in today's issue of the journal Nature.
Andolfatto and his colleagues examined DNA from the fruit fly Drosophila melanogaster. They confirmed that non-coding regions in DNA are strongly affected by natural selection. In other words, evolution has kept some of these DNA sections intact because they're beneficial to the species' continued survival.
Scientists have long believed genes are the main parts of DNA that evolve to generate new species. But in recent years, gene mapping projects have revealed that the genes of fruit flies, worms and humans are much more similar than researchers had expected, given the species' obvious physical differences.
The observation has led biologists to speculate that the ways in which genes are regulated, or when and how often they're activated, account for most of the evolutionary differences among species.
Andolfatto's study suggests it's the non-coding regions of DNA, at least in the fruit fly, that seem to play this regulatory role.
In their project, Andolfatto and colleagues amassed support for the idea that species contrast most dramatically in their non-coding sections of DNA.
Examining various species of Drosophila fruit flies, the researchers found that such sections differ from species to species. The implication is that changes to non-coding regions of DNA help to control the evolution of new species, the scientists said.
"(Gene-based) evolution has traditionally been emphasized as a key facet" of a species' change over time, Andolfatto said. "My results . . . demonstrate that non-coding, regulatory changes have also been of great importance."
Bruce Lieberman: (619) 293-2836; email@example.com