While Watson and Crick are celebrated worldwide for the discovery, there were other researchers who also worked on the structure of DNA at that time. On this point, the history gets controversial.
Rosalind Franklin and Maurice Wilkins were using a technique called X-ray diffraction to look for the geometry of DNA. In this method, scientists treated the DNA in a certain way so when they shined X-rays on it, they bounced off the sample and created patterns on photographic film. These patterns helped scientists infer the crystal's structures.
Franklin's "photograph 51," created using this method, indicated the helical structure of DNA to Watson and Crick, according to the official Nobel Prize website. But Watson remembers Franklin and her work differently -- it was eight months between her picture and the double helix discovery, and, according to Watson, Franklin did not want to investigate the possibility of a helical structure.
Franklin died at age 37 of ovarian cancer, before the Nobel Prize in physiology or medicine was awarded for the DNA structure discovery. The award is never given posthumously, and Franklin was never nominated, according to the Nobel Prize website.
The important problems
Colleagues of Watson say he's a big fan of hanging around smart people.
Watson and Crick were a history-making team, but they went their separate ways after the DNA double helix discovery. In 1956, Watson moved to Harvard.
Capecchi remembers that Watson taught him not to limit himself in terms of work that will make a difference.
"One of the mantras that I keep with me: It takes about the same amount of energy to work on a little problem as the big problems, so why waste your time on the little problems?" Capecchi said. "Put your efforts into significant problems."
Watson then directed the Long Island research institution from 1968 to 1993, overseeing its tremendous expansion into education and research, not to mention the installment of a statue of Charles Darwin looking out at the boats.
"We became one of the most prominent cancer researcher places in the country," said Bruce Stillman, president of Cold Spring Harbor Laboratory. "Just as he was with the double helix, he was a real visionary in running an institution, and how an institution can have an impact on the world."
The force of Watson's personality has influenced the development of the lab, said Jan Witkowski, a professor at Cold Spring Harbor Laboratory.
"He didn't tolerate fools," Witkowski said. "That includes in meetings."
Watson has been quoted in the past making controversial, unscientific claims about sensitive matters.
"He thinks very, very out of the box, and I think that's one of the penalties you get for thinking out loud about things and wondering about them," Stillman said. "He challenges people to think about issues, and you get into trouble doing that."
Watson also was the first director of the Human Genome Project, an international project aiming to sequence the human genome, but resigned in 1992. The project ended in 2003, establishing the order of the 3 billion letters in the genome, which can be thought of as "the book of life."
Between insights from the genome project and the double helix structure, DNA has proved to be important in surprising areas, Watson said, from DNA fingerprinting to diagnosing risk for genetic disease. DNA will probably be essential in future cures for cancer, because cancer arises from changes in DNA, Watson said.
"I don't want to die until I see cancer cured," he said with a laugh. "Because I think it could happen."
On the sunny grounds of Cold Spring Harbor, Watson dons a white floppy hat and glasses. These days, he's interested in how exercise prevents disease such as cancer, and says he has some unpopular ideas about antioxidants and diet.
Among Watson's current activities is writing a book about his father and his family called "Father to Son." He's learned that he descended from a Watson living in Springfield, Illinois, who decided to go on the Gold Rush.
When this ancestral Watson returned, he established a confectionery store where -- according to James Watson -- Abraham Lincoln used to buy desserts. The ancestor also founded a large resort hotel in the Midwest, which wouldn't have happened unless he'd taken a big chance to go look for gold.
As far as Watson, "DNA was my only gold rush," he said. "I regarded DNA as worth a gold rush."
Besides genetics and curing cancer, Watson has been thinking about his age. He used to not want to get to 90 because it's "hard to find role models" among that age group, and now he finds it hard to find desirable conversation partners among his peers.