Research reconstructs process that defined DNA structure – 04/25/2023 – Science

The discovery of the structure of DNA, which has just completed 70 years, has revolutionized our understanding of living beings, but has also been seen by the public and scientists as a historical injustice.

The laurels of the discovery went to the British Francis Crick and the American James Watson, winners of the Nobel Prize in Medicine. However, there were indications that they would have used, without permission, data obtained by the chemist Rosalind Franklin to formulate their famous model of the DNA molecule, that of the “double helix” or twisted ladder.

It would therefore be a classic case of academic misconduct and scientific machismo, due to the disregard for Franklin’s contribution. Newly found documents, however, indicate that the real picture that led to the historic discovery is more complex. Everything indicates that the researcher was aware of sharing her data with Watson and Crick and understood a good part of the implications of her work.

This is the thesis defended by a pair of historians of science, Matthew Cobb, from the University of Manchester (UK), and Nathaniel Comfort, from Johns Hopkins University (USA). In an article in the latest issue of the specialized journal Nature, the two reconstruct the process that led to the definition of the structure of DNA, now taking into account the new documents they brought to light.

“Franklin deserves to be remembered not as a victim of the double helix but as an equal contributor to the discovery of its structure,” they write.

Science historians usually consider that the process of elucidating the shape of the DNA molecule had its climax on April 25, 1953, with the publication of an article signed by Watson and Crick detailing their model. However, this work came on the heels of several years of work during which Franklin had made crucial contributions.

Evidence that DNA was capable of containing the “recipe” for the characteristics of cells and living organisms as a whole had been strong since the 1940s, but no one still had any idea how this could happen. Many scientists thought that DNA was too simple a molecule for this function, because of its apparently repetitive nature, which succeeds with small variations.

To better understand how the molecule worked, it was crucial to understand its structure. Rosalind Franklin, who started working at King’s College London from 1951 onwards, began to face this problem through the technique of X-ray crystallography. In this process, the molecule to be studied is transformed into its crystalline form and bombarded with X-rays. At the time, this was done in front of a photographic plate, which produced a specific pattern of images. This “picture”, in turn, was interpreted in order to estimate the most likely shape of the molecule under analysis.

Based on reports such as that of James Watson himself, in his autobiographical book “The Double Helix”, the idea was consolidated that Franklin had produced the most important image of DNA so far, the so-called Photograph 51. She, however, did not would have been able to correctly interpret this crystallographic image. Franklin’s then-boss Maurice Wilkins allegedly showed Watson the crystallography without permission, which in turn allowed him and Crick to finally elucidate the nature of the DNA double helix.

According to Cobb and Comfort, however, the scenario described in the last paragraph is a very simplistic reconstruction of what really happened. They recall that the main data obtained by Franklin had already been shared openly between the leadership of her laboratory and that of the University of Cambridge where Watson and Crick worked.

In addition, historians have found a January 1953 letter written by Pauline Cowan, Franklin’s colleague at King’s College, inviting Crick to a lecture by the author of Photograph 51 on her work with DNA crystallography. At the same time, Cowan says that Crick’s boss had probably already passed on the most important parts of the talk’s content to him. Therefore, it is most likely that Franklin’s findings were already openly circulating among the British scientific community, without the need for Watson and Crick to outsmart the researcher.

Furthermore, say the authors of the article, Watson and Crick spent six weeks independently trying to assemble their model of the structure of DNA, using chemical calculations and pieces of cardboard. “They didn’t steal the data from the King’s College group and magically solve the DNA structure. In fact, they assembled the structure using their own approach and then used the data [de Franklin] to confirm it”, they summarize.

Documentation from the 1950s also shows that Franklin had realized one of the essential properties of DNA: the fact that the repetition of units, in different combinations, could function as an alphabet, a book that would store genetic information. So she was also getting closer to understanding the nature of her data, contrary to what many people still believe.

One of the reasons Watson and Crick ended up beating her was that the relatively few female scientists at the time tended to be left out of informal conversations between researchers where the exchange of ideas continued after hours. In her time, for example, there were other female scientists at King’s College, but they weren’t allowed into the university’s “common room”—a space where male researchers could gather in their spare time.

“What Franklin lacked was what Watson and Crick had: each other, someone to talk to, discuss and reason with. It’s incredible that she’s managed to get as far as she did practically alone,” Cobb told the Sheet.

She eventually died of cancer in 1958, aged just 37. The Nobel Prize for discovering the structure of DNA came in 1962, and it was passed over, in part, because the prize is given only to living scientists.