For most scientists, a Nobel Prize is the capstone of a career.

But in the 50 years since their breakthrough discovery of the structure of DNA, James D. Watson and Francis H.C. Crick have continued to pursue the frontiers of knowledge, albeit along different paths.

Watson, once the brash whiz kid from Chicago, has become the "dean of DNA," as one colleague calls him. Buoyed by his gossipy 1968 bestseller The Double Helix, he abandoned his laboratory bench for an administrator's desk, pushing for a cancer cure and a complete map of the human genome.

He stands today as the most visible figure in the continuing genetics revolution, though his penchant for speaking his razor-sharp mind has left a trail of enemies — and admirers.

Crick, who was raised in a middle-class English family, remains a researcher at 86 and co-wrote yet another scientific paper that was published just last month.

After the 1953 coup, Crick pushed on to work out the mechanics of DNA before his restless mind led him to explore more cosmic questions, such as the origins of life on Earth. For the past two decades, he has searched for the scientific basis of human consciousness.

As the world marks the 50th anniversary of the discovery of the double helix with celebrations this week in New York and this spring in England, Australia and elsewhere, admirers are honoring Watson's and Crick's lifelong contributions to science, not merely the discovery that earned them the 1962 Nobel Prize.

At 74, Watson crisscrosses the country attending scientific meetings and ceremonies. In rambling lectures and interviews, he extols the promise of genetic research even as he recalls with self-deprecating humor how he and Crick made history.

"I think the biggest opportunity is curing cancer," he said recently while sipping coffee in his office at Cold Spring Harbor Laboratory in New York. "We really know a lot about that disease."

Watson is president of Cold Spring Harbor, the former biological field station on the north shore of Long Island that he took over in 1968 and steered toward a genetic cure for cancer. He relinquished administrative oversight nine years ago, but the institution's 350 researchers remain among the most frequently cited in scientific literature.

His wispy white hair remains as unruly as it was in his youth, as does his willingness to say whatever comes to mind.

"I think it's very important to study intelligence," he said in a recent lecture, acknowledging the notion's political incorrectness. "Some people are stupid because of their genes."

Watson recalls growing up poor on the south side of Chicago, where he absorbed his parents' philosophical skepticism. "Don't believe anything unless there is evidence," he says.

An avid bird-watcher in his youth, he was drawn to molecular biology by a book on genetics that he read at the University of Chicago — the same book that inspired his future partner, Crick.

As a researcher, Watson never achieved another breakthrough on the level of the double helix, despite nearly 20 years of lab work. Instead, he evolved into a scientific talent scout who attracted bright young minds and motivated them.

But Watson's passion for molecular biology — and, to some, his arrogance — got him into scrapes over the years. In the 1950s, while carving out a molecular biology department at Harvard University, he clashed with Edward O. Wilson, a Pulitzer Prize-winning author and noted expert on ants.

"I found him the most unpleasant human being I ever met," Wilson wrote in his memoir, Naturalist, dubbing Watson the "Caligula of biology."

Wilson and others, however, came to respect Watson's administrative abilities.

"The way he built up Cold Spring Harbor Laboratory was just extraordinary," says Dr. Victor A. McKusick, a pioneer of medical genetics at the Johns Hopkins University.