Photo 51
Encyclopedia
Photo 51 is the nickname given to an X-ray diffraction image of DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 taken by Rosalind Franklin
Rosalind Franklin
Rosalind Elsie Franklin was a British biophysicist and X-ray crystallographer who made critical contributions to the understanding of the fine molecular structures of DNA, RNA, viruses, coal and graphite...

 in 1952 that was critical evidence in identifying the structure of DNA. The photo was taken by Franklin while working at King's College London
King's College London
King's College London is a public research university located in London, United Kingdom and a constituent college of the federal University of London. King's has a claim to being the third oldest university in England, having been founded by King George IV and the Duke of Wellington in 1829, and...

 in Sir John Randall
John Randall (physicist)
Sir John Turton Randall, FRS, FRSE, was a British physicist and biophysicist, credited with radical improvement of the cavity magnetron, an essential component of centimetric wavelength radar, which was one of the keys to the Allied victory in the Second World War. It is also the key component of...

's group.

James D. Watson
James D. Watson
James Dewey Watson is an American molecular biologist, geneticist, and zoologist, best known as one of the co-discoverers of the structure of DNA in 1953 with Francis Crick...

 was shown the photo by Maurice Wilkins
Maurice Wilkins
Maurice Hugh Frederick Wilkins CBE FRS was a New Zealand-born English physicist and molecular biologist, and Nobel Laureate whose research contributed to the scientific understanding of phosphorescence, isotope separation, optical microscopy and X-ray diffraction, and to the development of radar...

, who had been given it by Raymond Gosling
Raymond Gosling
Raymond Gosling is a distinguished scientist who worked with both Maurice Wilkins and Rosalind Franklin at King's College London in deducing the structure of DNA, under the direction of Sir John Randall. His other KCL colleagues included Alex Stokes and Herbert Wilson.-Early years:He was born in...

; along with Francis Crick
Francis Crick
Francis Harry Compton Crick OM FRS was an English molecular biologist, biophysicist, and neuroscientist, and most noted for being one of two co-discoverers of the structure of the DNA molecule in 1953, together with James D. Watson...

, he used Photo 51 to develop the first chemical model of DNA, for which the three men jointly won the 1962 Nobel Prize in Physiology or Medicine
Nobel Prize in Physiology or Medicine
The Nobel Prize in Physiology or Medicine administered by the Nobel Foundation, is awarded once a year for outstanding discoveries in the field of life science and medicine. It is one of five Nobel Prizes established in 1895 by Swedish chemist Alfred Nobel, the inventor of dynamite, in his will...

. As the Nobel prize is not awarded posthumously, Franklin, who had died in 1958, was not eligible for nomination.

The photograph provided key information that was essential for developing a model of B-form (hydrated) DNA. In particular, it could be determined from the diffraction pattern, and was openly discussed by Franklin in lectures attended by Watson and in reports accessible to Watson and Crick, that DNA (1) was helical, (2) was likely a double helix with antiparallel strands, and, (3) had the phosphate backbone on the outside (thus the bases of DNA, which are the "code" for inheritance, were on the inside of the helix). Calculations from the photograph also provided crucial parameters for the size of the helix and its structure, all of which were critical for the molecular modeling undertaken by Watson and Crick..

Photo 51 was, therefore, the critical data that led to the model and confirmation of the postulated double helical structure of DNA, published during 1953 in a series of five articles in the journal Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...

. Franklin and Raymond Gosling's own publication in the same issue of Nature was the first publication of this more clarified X-ray image of DNA.

As historians of science have re-examineed 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 her image, is a hotly debated topic, made more controversial by the negative caricature of Franklin presented in Watson's history of the research on DNA structure, "The Double Helix
The Double Helix
The Double Helix: A Personal Account of the Discovery of the Structure of DNA is an autobiographical account of the discovery of the double helix structure of DNA written by James D. Watson and published in 1968. It was and remains a controversial account...

." Watson later admitted his distortion of Franklin in his book, noting in a preface to a later edition: "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."

Cultural references

  • A play by the title Photograph 51 focuses on the role of x-ray crystallographer Rosalind Franklin in the discovery of the structure of DNA. This play won the 3rd STAGE
    Scientists, Technologists and Artists Generating Exploration
    Scientists, Technologists and Artists Generating Exploration was created in 2005 to encourage collaboration between artists and scientists. Originally, it began as a partnership between the Professional Artists Lab and the California NanoSystems Institute at the University of California, Santa...

     International Script Competition, and a film version is being produced by Darren Aronofsky
    Darren Aronofsky
    Darren Aronofsky is an American film director, screenwriter and film producer. He attended Harvard University to study film theory and the American Film Institute to study both live-action and animation filmmaking...

    , Rachel Weisz
    Rachel Weisz
    Rachel Hannah Weisz born 7 March 1970)is an English-American film and theatre actress and former fashion model. She started her acting career at Trinity Hall, Cambridge, where she co-founded the theatrical group Cambridge Talking Tongues...

    and Ari Handel.
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