Photo 51 is the nickname given to an X-ray diffraction image of crystallized DNA taken by Rosalind Franklin and her PhD student Raymond Gosling in May 1952 at King's College London, while working in Sir John Randall's group. It was critical evidence in identifying the structure of DNA.
James Watson was shown the photo by his collaborator, Maurice Wilkins, without Rosalind Franklin's approval or knowledge. Wilkins did this, as by this time, Gosling had returned under his supervision, as Franklin was leaving King's and Randall had asked Gosling to share all his data with Wilkins. Along with Francis Crick, Watson used characteristics and features of Photo 51, together with evidence from multiple other sources, to develop the chemical model of the DNA molecule. Their model, and manuscripts by Wilkins and colleagues, and Gosling and Franklin, were first published, together, in 1953, in the same issue of Nature. In 1962, the Nobel Prize in Physiology or Medicine was awarded to Watson, Crick and Wilkins. The prize was not awarded to Franklin; she had died four years earlier, and although there was not yet a rule against posthumous awards, the Nobel Committee generally does not make posthumous nominations.
The photograph provided key information that was essential for developing a model of DNA. The diffraction pattern determined the helical nature of the double helix strands (antiparallel). The outside of the DNA chain has a backbone of alternating deoxyribose and phosphate moieties, and the base pairs, the order of which provides codes for protein building and thereby inheritance, are inside the helix. Watson and Crick's calculations from Gosling and Franklin's photography gave crucial parameters for the size and structure of the helix.
Photo 51 became a crucial data source that led to the development of the DNA model and confirmed the prior postulated double helical structure of DNA, which were presented in the articles in the Nature journal by Raymond Gosling.
As historians of science have re-examined the period during which this image was obtained, considerable controversy has arisen over both the significance of the contribution of this image to the work of Watson and Crick, as well as the methods by which they obtained the image. Franklin was hired independently of Maurice Wilkins, who, nonetheless, showed Photo 51 to Watson and Crick, without her knowledge. Whether Franklin would have deduced the structure of DNA on her own, from her own data, had Watson and Crick not obtained Gosling's image, is a hotly debated topic, made more controversial by the negative caricature of Franklin presented in the early chapters of Watson's history of the research on DNA structure, The Double Helix. Watson admitted his distortion of Franklin in his book, noting in the epilogue: "Since my initial impressions about [Franklin], both scientific and personal (as recorded in the early pages of this book) were often wrong, I want to say something here about her achievements."
- A 56-minute documentary DNA - Secret of Photo 51, was broadcast in 2003 on PBS NOVA. Narrated by Barbara Flynn, the program features interviews with Wilkins, Gosling, Aaron Klug, Brenda Maddox, including Franklin's friends Vittorio Luzzati, Caspar, Anne Piper, and Sue Richley. The UK version produced by BBC is titled Rosalind Franklin: DNA's Dark Lady.
- The first episode of a PBS documentary serial, DNA, which aired on 4 January 2004 as "The Secret of Life", centres on and features the contributions of Franklin. Narrated by Jeff Goldblum, it features Watson, Wilkins, Gosling and Peter Pauling (son of Linus Pauling).
- A play entitled Photograph 51 by Anna Ziegler focuses on the role of x-ray crystallographer Rosalind Franklin in the discovery of the structure of DNA. This play won the 3rd STAGE International Script Competition in 2008. In 2015, the play was put on at London West End, with Nicole Kidman playing Franklin.
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- Cox, Gordon (April 23, 2015). "Nicole Kidman to Star on West End in 'Photograph 51'". Variety. Retrieved 25 August 2015.
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- Porteous, Jacob (24 April 2015). "Nicole Kidman Returns To The West End In Photograph 51". London Theatre Direct. Retrieved 27 October 2015.