In the October 20 issue of Nature, Peter Andolfatto, an assistant professor of biology at UCSD, shows that these non-coding regions play an important role in maintaining an organism's genetic integrity. In his study of the genes from the fruit fly Drosophila melanogaster, he discovered that these regions are strongly affected by natural selection, the evolutionary process that preferentially leads to the survival of organisms and genes best adapted to the environment.
Andolfatto's findings are important because the similarity of genome sequences in fruit flies, worms and humans suggest that similar processes are probably responsible for the differences between humans and their close evolutionary relatives.
"Sequencing of the complete genome in humans, fruit flies, nematodes and plants has revealed that the number of protein-coding genes is much more similar among these species than expected," he says. "Curiously, the largest differences between major species groups appear to be the amount of 'junk' DNA rather than the number of genes."
Using a recently developed population genetic approach, Andolfatto showed in his study that these expansive regions of "junk" DNA--which in Drosophila accounts for about 80 percent of the fly's total genome--are evolving more slowly than expected due to natural selection pressures on the non-protein-coding DNA to remain the same over time.
"This pattern most likely reflects resistance to the incorporation of new mutations," he says. "In fact, 40 to 70 percent of new mutations that arise in non-coding DNA fail to be incorporated by this species, which suggests that these non-prote
Contact: Kim McDonald
University of California - San Diego