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How did Rosalind Franklin contribute to solve the DNA structure?

Today I would like to make a brief interruption on the posts about my path on the biological field and I would like to celebrate the day of women in science, that was on the 11th of February. To do so, and since on my last two posts I talked about the DNA, I would like to tell you how the DNA was discovered (and the role of a very famous woman scientist, Rosalind Franklin).

Even though James Watson, Francis Crick and Maurice Wilkins received the Nobel Prize in Physiology or Medicine in 1962 “for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material”, the story of the discovery of DNA begins in the 1800s, when a Swiss chemist called Johann Friedrich Miescher found a mysterious substance that he called ‘nuclein’, because he believed it came from the cell nucleus. It was then only in 1881 that Albrecht Kossel, a German biochemist, isolated the four nucleotide bases (A-T-G-C) that are the building blocks of DNA, a work that was awarded with the in 1910 when he received the Nobel Prize in Physiology or Medicine. Thanks to these previous experimental findings and to several scientific breakthroughs, such as the progress made by X-ray crystallographers, the three aforementioned scientists and Rosalind Franklin were able to solve the structure of the DNA. However, as I have already mentioned, only the male scientists received the Nobel Prize. But let’s talk about Rosalind Franklin and let’s try to figure out why she was excluded from this prize.

Rosalind Franklin was born into a London banking family, where all the children—girls and boys—were encouraged to develop their individual aptitudes. She therefore completed her degree in Chemistry in 1941, in the middle of World War II, and undertook graduate work at Cambridge with Ronald Norrish, a future Nobel laureate. After contributing to the war effort at the British Coal Utilization Research Association, where she performed investigations on the properties of coal and graphite, she came back to Cambridge where she presented a dissertation based on this work and was granted a PhD in Physical Chemistry. After the war she went to Paris at the Laboratoire Centrale des Services Chimiques de l’Etat where she was introduced to the technique of X-ray crystallography and rapidly became a respected authority in this field. In 1951 Franklin joined the Biophysical Laboratory at King’s College where she started using the X-ray diffraction methods to study the DNA. She soon discovered the density of DNA and, more importantly, established that the molecule existed in a helical conformation. Her work to make clearer X-ray patterns of DNA molecules laid the foundation for Watson and Crick to suggest in 1953 that the structure of DNA is a double-helix polymer, a spiral consisting of two DNA strands wound around each other. Unfortunately, Franklin’s involvement in cutting-edge DNA research was halted by her death from cancer in 1958.

Sadly, during her work, Franklin experienced the sexism of science firsthand. Already when she graduated from the University of Cambridge in 1941 women were still not recognised as full members of the university or entitled to a degree award. She also had to protest against lower pay compared to her male colleagues and her lack of promotion even when she was publishing work in the top scientific journals. Moreover, the key image that revealed the double helix structure of DNA, known as “Photograph 51”, was taken by Franklin and her PhD student Raymond Gosling at King’s College London in May 1952, but it was her colleague Wilkins that then showed this iconic image to Watson at Cambridge without Franklin’s knowledge or consent (see picture below).

Rosalind Franklin and the famous “Photograph 51” that helped reavoling the double helix structure of DNA. Modified from

Watson and Crick also gained access to a King’s report that Franklin had helped prepare, which contained extra experimental information that Crick crucially recognised as the final piece of the puzzle. However, she kept on working on other projects until she died at the age of 37 and Franklin herself seemed to see her work as her real success. She composed an inscription for her gravestone in Willesden Cemetery in London that says: “Her Research and Discoveries on Viruses Remain of Lasting Benefit to Mankind.”

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