: [POST-BROADCAST CLARIFICATION: This story, which includes excerpts from a story that aired in 1993, neglects to mention the significant contribution of scientist Rosalind Franklin, who produced the crucial X-ray photograph of DNA that was later used by Watson and Crick. Franklin is widely acknowledged as playing a major role in the discovery of DNA's double helix structure, and, in fact, published a paper on her findings that accompanied Watson and Crick's research.]
AILSA CHANG, HOST:
Seventy years ago, two scientists had a flash of insight that changed the world. On February 28, 1953, James Watson and Francis Crick discovered the structure of DNA, the now-famous double helix. Their discovery helped unlock the mystery of our genetic code, and it helped us understand what makes us us. Here's NPR correspondent Joe Palca from 1993, commemorating the anniversary of this groundbreaking discovery.
JOE PALCA, BYLINE: Watson and Crick made an unlikely pair in 1951, when they met. The tall, gangly Watson, with an unruly shock of hair, was just 23 years old, with a doctorate from Indiana University. Crick was 12 years older, but still a graduate student at Cambridge in England.
JAMES WATSON: I'm sure Francis and I talked about guessing the structure of DNA within a half hour of probably meeting. I mean, it was the thing I wanted to do. Certainly, Francis did all the thinking, and I had sort of the goal.
FRANCIS CRICK: It isn't true...
WATSON: I know (ph).
CRICK: ...That I did all the thinking. But you should make the general observation that two people are better than one.
PALCA: In 1953, scientists knew there had to be some chemical in cells that transmitted genetic information from one generation to the next. But no one knew what that chemical looked like or how it worked. Some scientists were betting that chemical might be deoxyribonucleic acid, better known as DNA. Watson and Crick were in the DNA camp. They hoped that by figuring out the three-dimensional structure of DNA, they would show that this was the chemical that contained the blueprint for life. The pair set about building models of DNA using a chemist's equivalent of a child's Tinkertoy set. Earlier experiments using X-rays had determined the shapes the Tinkertoy models could take.
WATSON: It could have been on Friday when we found base pairs. But then the following Monday, you started building the model.
CRICK: It could be. It could be, Jim. You probably got the days right.
WATSON: And then it took, I think, about a week before...
CRICK: It was three...
WATSON: ...Or four or five days.
CRICK: Yes. Three or four.
WATSON: When you were satisfied, you had the plumb line, and you were measuring the coordinates.
PALCA: Both agree it was a moment of euphoric insight when they realized that DNA was a two-stranded molecule twisted into a helix. When word of their achievement began to circulate, scientists from around the world descended on the Cavendish Lab at Cambridge, where Crick and Watson were working.
CRICK: We did have a constant stream of visitors, so much so that Jim got sick of me 'cause I was in the state of - somewhat of euphoria...
WATSON: Yes.
CRICK: ...Explaining all this. And Jim would have to go out of the room. He couldn't bear to hear it all over again.
WATSON: Well, I thought, you know, it was so obvious, you didn't have to talk about it, you know?
PALCA: Since their discovery, the pace of science has been dizzying. An entire new area of biology has opened up. Scientists now know at the most fundamental level what genes do and how to manipulate them. I'm Joe Palca reporting.
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