DNA "The Secret of Life" 28th February 1953

For decades the Eagle was the local pub for scientists from the nearby Cavendish Laboratory at Cambridge University. It was there on 28 February 1953 that Francis Crick and James Watson, who had been working at the laboratory that day, celebrated the discovery of the structure of DNA.

The Eagle Inn has a long history as a significant part of the Cambridge scene. Some of its timbers as well as its name go back to the 16th century. During the great era of the stagecoach, visitors rolled in underneath its arch after a long day’s journey up from London.

The property was acquired by neighbouring Corpus Christi College, and in the twentieth century the accommodation was taken over as student lodgings. The pub occupied rooms at the back of the yard, where locals, visitors and students enjoyed its traditional atmosphere. During World War II American servicemen based in the area gathered in the bar, and wrote names and service numbers on the ceiling in smoke – now preserved under varnish.

By the 1950s the University Cavendish Laboratory had long been famous for pioneering work on the structure of the atom. It had also become, in 1947, the temporary home of a Medical Research Council Unit, researching the structure of biological molecules. Francis Crick joined the Unit in 1949, having shifted his interests from physics to chemistry and thence to biology. Two years later a young American biologist, James Watson, joined the team. He had attended a conference that year, 1951, in Naples at which he had seen X-ray diffraction pictures of DNA. DNA (deoxyribonucleic acid) was one of the subjects of the moment for biologists looking at molecular structure. It was realised that somehow the structure of DNA was crucial to how living cells replicated. The work of Linus Pauling in America and of Maurice Wilkins at King’s College London (who had shown the X-ray picture) was moving towards identifying the precise structure: possibly a helix, but what were the components, how did they fit together and how could the form reproduce itself?

Crick and Watson found themselves sharing an office in the Cavendish and an enthusiasm for this puzzle. Drawing together the clues from published research, they also made contact with Wilkins again, and the work being done by Rosalind Franklin and her research student Raymond Gosling. Franklin, a Cambridge graduate of Newnham College, was working in Wilkins’s team at King’s, but the relationship was an unhappy one, lacking the constructive collaboration that Watson and Crick enjoyed. She was concentrating on X-ray diffraction to examine the structure of DNA, and described her findings at a colloquium in November 1951. On this basis, Watson and Crick constructed a model of the structure. When they invited her to see it, Franklin pointed out a number of errors. Watson had not remembered her findings accurately enough.

There was a pause of several months until information from other experiments reached them, and they returned to considering how the chemicals in DNA - adenine, thymine, guanine and cytosine, or A, T, G and C could fit the information they had. Further photographs from King’s helped, in particular Photo 51, a high-quality X-ray diffraction image taken by Raymond Gosling, a graduate student working under the supervision of Rosalind Franklin, in May 1952. They showed more clearly the size of the molecules and the helical construction. Watson pursued the idea of pair bondings that might fit the two-chain helical structure deduced by Crick. With the physical aid of cardboard cut-outs a possible pattern emerged, which they constructed in a model as a double helix. Everything fitted.

On 28 February 1953 Crick announced dramatically in the Eagle pub that they had found the secret of life. The formal scientific presentation of their results, with those of Wilkins and Franklin, appeared in Nature in April 1953.

In 1962 Crick, Watson and Wilkins were awarded the Nobel Prize for Medicine “for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material”. (Rosalind Franklin had died of cancer in 1958, and as the Prize is never given posthumously was not able to share the credit that was her due.) Their work initiated a flood of further research round the globe to read in detail the secrets of the code of life.

The MRC Unit moved out of the Cavendish to the School of Medicine where it became the MRC Laboratory of Molecular Biology. A large model representing the double helix can be seen through its window, at the building on the Addenbrooke’s site.

Professor Watson unveiled another representation of the double helix in November 2005 in the grounds of Clare College.

The first blue plaque celebrating this event was unveiled by James Watson in 2003 but it provoked debate because it made no mention of Rosalind Franklin, whose scientific work provided data on which the discovery relied. In recent years there have been efforts to increase awareness of the role played by important female scientists, whose work has sometimes been overshadowed by their male colleagues. Rosalind Franklin was one such scientist and so the DNA plaque without her name became emblematic of this cause. To the extent it had been graffitied with ‘+ Franklin’ (see photo below). Over time the condition of the plaque had deteriorated and we decided to replace it, and this gave us the opportunity to recognise the work of Franklin, Maurice Wilkins and others, as well as that of Crick and Watson.

The new plaque was unveiled by Professor Christopher Howe at a ceremony at Corpus Christi College/The Eagle in August 2023.