What is the purpose of noncoding DNA?
A typical human cell contains more than 6 feet of tightly cornrowed DNA. But only about an inch of that carries the codes needed to make proteins, the day laborers of biology. What's the other 71 inches?
It's junk, Nobelist Sydney Brenner said after it was discovered back in the 1970s. The name stuck, but biologists have known for a while that the junk DNA must contain treasures. If noncoding DNA were just along for the ride, it would rapidly incorporate mutations. But long stretches of noncoding DNA have remained basically the same for many millions of years - they must be doing something.
Now scientists are starting to speculate that proteins, and the regular DNA that creates them, are just the nuts and bolts of the system. "They're like the parts for a 757 jet sitting on the floor of a factory," says University of Queensland geneticist John Mattick. The noncoding DNA is likely "the assembly plans and control systems." Unfortunately, he concludes, because we've spent 30 years thinking of it as junk, we're just now learning how to read it.
- Steve Olson
