How One Photo Changed Everything - The Story Of Photo 51

The story of DNA. One that has twists and turns and unexpected discoveries but ultimately represents the power of the human race and how we have the knowledge to change the world. I'm sure you’ve heard of Watson and Crick - the two scientists who “solved” DNA, but are they really solely responsible for the discovery of the structure of DNA or were there other, more unsung, heroes who sat behind the scenes and worked tirelessly to discover the beautiful code of life. 

To get a background of how exactly Rosalind Franklin took the all important photo 51, we have to delve into her past. Rosalind Franklin was born in 1920 and attended the University of Cambridge where she lived and breathed chemistry. After she graduated, she received a fellowship to commence research at the university of Cambridge. Moments after starting her research, World War II had hit and she decided to change her path and instead serve as an air warden in London and later giving up her fellowship entirely to instead study the properties of carbon and specifically coal to help the war effort. Proceeding this, Franklin studied X-ray diffraction technology in Paris and later in King’s College London she used these findings in the field of X-ray diffraction to the study of DNA. 

Why is Franklin not as mentioned in regards to DNA as Watson and Crick?

Rumour has it that the idea of Watson and Cricks double helix came when they were shown Franklin's picture depicting an X-ray image of DNA without her permission. This image was dubbed ‘photograph 51’ and was treated as the all important key to life. Soon after, Franklin died at the young age of 37 from ovarian cancer which likely came from her dedication to science and X-ray crystallography meaning that she was unable to portray how she understood her data. It was said that she remained unable to decipher her own data and photographs and she simply pondered on it for months. However, this isn’t how the story of DNA was actually carried out. News articles that went unpublished from Franklin suggest that she in fact DID grasp the structure of DNA and was just as much a contributor as to Crick and Watson. This story has such great meaning in today's world as we appreciate the role of women in science and how they were so readily and often subjugated and discriminated against. We can also look at the influence of men in science - for example looking at sexism within scientific terminology itself - for example; daughter cells? Sister chromatids? It is also important to note that I’m not suggesting that we necessarily need to change the words we have in science today but more so to understand where they come from and the people who have been pushed to the side in the past. 

So what actually happened with photo 51?

Previous scientists had led the foundation for the discovery of the structure of DNA, namely Miescher, Levene and Chargaff. They found that all living things contain DNA, that the quantity of purines is equal to the number of pyrimidines and consequently the bases adenine and thymine pair together and guanine with cytosine. All well and good but the physical structure of DNA (the double helix) still remained a mystery. At King's College, Franklin and Wilkins worked to uncover DNA. With a very pure DNA sample from the Swiss chemist Rudolf Signer, Franklin was able to able to realise that DNA in solution could take to different forms - crystalline (A form) and paracrystalline (B form) and that she could convert A to B by simply raising the relative humidity of the solution and visa versa. After this discovery, the only logical thing to do was to give the A form to Franklin and the B form to Wilkins and allow each to research respectively, especially given the fact that they didn’t work too well together. The crystalline form was the obvious choice to research for a scientist. When fired with X-rays the image produced was clear and sharp which consequently meant a more accurate picture and more accurate data. The B form was the opposite - more blurry and less detailed but a comparatively more detailed analysis. Her analysis of both the A and B form led her to go back and forth from the idea of DNA being helical and often getting ridiculed for it. She saw the B, more humid, form of DNA as being an artefact of water and not an accurate depiction of DNA leading her to reject her original helical proposal. In terms of chemistry, the A form was the most logical type of DNA to study; however by choosing this, she ignored the intrinsically wet nature of the cell and that the B form would be the one of prevalence inside a cell.

Long story short, if a helix is viewed from the side, it shows a recurring zig-zag pattern which will cause a number of diffraction spots at right angles to each other. Hence in photo 51, a distinctive cross pattern can be seen. When Watson saw this photo, him and Crick built a model using a double helix structure and found that it was the perfect shape that fit all of the necessary properties. I think Rosalind Franklin was one of the greatest scientists to ever come about who gave her life to scientific research and was a strong female despite the criticism of her male peers. She is truly an example for us all to live by.

Bibliography

[1] - Discovery of DNA double helix: Watson and Crick | Learn Science at Scitable. (n.d.). https://www.nature.com/scitable/topicpage/discovery-of-dna-structure-and-function-watson-397/

[2] - Cobb, M. (2018, February 14). Sexism in science: did Watson and Crick really steal Rosalind Franklin’s data? The Guardian. https://www.theguardian.com/science/2015/jun/23/sexism-in-science-did-watson-and-crick-really-steal-rosalind-franklins-data

[3] - Photograph 51, by Rosalind Franklin (1952) | Embryo Project Encyclopedia. (2019, December 30). https://embryo.asu.edu/pages/photograph-51-rosalind-franklin-1952

[4] - King’s College London. (n.d.). The story behind Photograph 51. https://www.kcl.ac.uk/the-story-behind-photograph-51

[5] - From the archive: Rosalind Franklin’s famous Photo 51. (2023, April 25). https://www.ukri.org/blog/from-the-archive-rosalind-franklins-famous-photo-51/

[6] - Cobb, M., & Comfort, N. (2023). What Rosalind Franklin truly contributed to the discovery of DNA’s structure. Nature, 616(7958), 657–660. https://doi.org/10.1038/d41586-023-01313-5