RNA, Not DNA, Is the Key to Life

DNA holds our genetic blueprints, but its cousin, RNA, conducts our daily lives

- Philip Ball

IN 1957, JUST FOUR YEARS AFTER Francis Crick and other scientists solved the riddle of DNA’s structure—the now famous double helix—Crick laid out what he called the “central dogma” of molecular biology, which his colleague James Watson later said implied that biological information flows inexorably from DNA to RNA to proteins. Although Watson was oversimplifying, the message was that the purpose of the double helix in our chromosomes is to hold, in encoded form, blueprints for the proteins that build and maintain our bodies. DNA’s chemical cousin, RNA, was the messenger that carries DNA instructions from the double helix in the cell’s nucleus to the protein-making machinery, called the ribosome, scattered around the cell.

Molecular biology’s mission, it seemed, was to decipher those genetic instructions. But in recent years researchers have discovered a dizzying array of “noncoding” RNA (ncRNA) molecules that do something other than ferry DNA instructions for proteins. They perform a surprisingly wide range of biochemical functions. It now seems that our genome may be at least as much a repository of plans for vital, noncoding RNA as it is for proteins. This shift in thinking has been “revolutionary,” says Thomas Cech, who shared the 1989 Nobel Prize in Chemistry with Sidney Altman for discovering RNA molecules, called ribozymes, that can catalyze biochemical reactions. “DNA is old stuff, 20th-century stuff,” Cech says. “It’s a one-trick pony. All it does is store biological information, which it does exquisitely well. But it’s inert—it can’t do anything without its children, RNA and proteins.”