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The Discovery of DNA's Structure

Taken in 1952, this image is the first X-ray picture of DNA, which led to the discovery of its molecular structure by Watson and Crick. Created by Rosalind Franklin using a technique called X-ray crystallography, it revealed the helical shape of the DNA molecule. Watson and Crick realized that DNA was made up of two chains of nucleotide pairs that encode the genetic information for all living things.

Credits: Photo of Rosalind Franklin courtesy of Vittorio Luzzati. Photo of x-ray crystallography (Exposure 51) courtesy of King's College Archives. King's College London.

The Discovery of DNA's Structure

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Evolution Since Darwin

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The Discovery of DNA's Structure:

They were hardly modest, these two brash young scientists who in 1953 declared to patrons of the Eagle Pub in Cambridge, England, that they had "found the secret of life." But James Watson and Francis Crick's claim was a valid one, for they had in fact discovered the structure of DNA, the chemical that encodes instructions for building and replicating almost all living things. The stunning find made possible the era of "new biology" that led to the biotechnology industry and, most recently, the deciphering of the human genetic blueprint.

Watson and Crick's discovery didn't come out of the blue. As early as 1943 Oswald Avery proved what had been suspected: that DNA, a nucleic acid, carries genetic information. But no one knew how it worked.

By the early 1950s, at least two groups were hot on the trail. Crick, a British graduate student, and Watson, an American research fellow, were in the hunt at Cambridge University.

At King's College in London, Rosalind Franklin and Maurice Wilkins were studying DNA. Wilkins and Franklin used X-ray diffraction as their main tool -- beaming X-rays through the molecule yielded a shadow picture of the molecule's structure, by how the X-rays bounced off its component parts.

Franklin, a shy and inward young woman, suffered from patronizing attitudes and sexism that forced her to do much of her work alone. And her senior partner, Wilkins, showed some of Franklin's findings to Watson in January 1953 without her knowledge.

Referring to Franklin's X-ray image known as "Exposure 51," James Watson is reported to have said, "The instant I saw the picture, my mouth fell open and my pulse began to race." Shortly after, Watson and Crick made a crucial advance when they proposed that the DNA molecule was made up of two chains of nucleotides paired in such a way to form a double helix, like a spiral staircase. This structure, announced in their famous paper in the April 1953 issue of Nature, explained how the DNA molecule could replicate itself during cell division, enabling organisms to reproduce themselves with amazing accuracy except for occasional mutations.

For their work, Watson, Crick, and Wilkins received the Nobel Prize in 1962. Despite her contribution to the discovery of DNA's helical structure, Rosalind Franklin was not named a prize winner: She had died of cancer four years earlier, at the age of 37.

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