Scientists differ on how to identify the structure of genetic material

The chemical structure of DNA, which is the genetic material of the chromosomes inside the cell’s nucleus

The race for DNA synthesis became particularly heated between the laboratory of Sir Lawrence Bragg (1890-1971) and the Imperial Medical Research Laboratories at Caltech, California, USA. London College, where researcher Rosalind Franklin worked under the guidance of scientist Sir John Randall (1905-1984).

Irish-born New Zealand scientist Maurice Hugh Frederick Wilkins (1916-2004) worked at Imperial College London in X-ray DNA from 1948 in collaboration with the young researcher Raymond Gosling (1926-2015).

Although Wilkins was a physicist, he was interested in the application of physical methods to the study of organic matter and is considered one of the founding pioneers of biophysics. Wilkins studied the structure of nucleic acids by imaging X-ray diffraction on their molecules. His images were not clear until he obtained good DNA samples from the Swiss Rudolf Signer (1903-1990), then a professor of organic chemistry at the University of Bern.

Wilkins and Gosling used simple instruments to X-ray the new samples of DNA, and the initial images in the 1950s showed a regular pattern in its structure, similar to the regular arrangement of atoms in crystals of minerals and salts. Wilkins and Gosling presented their initial images at a 1951 conference in Naples, Italy. Among those present was a young American biologist looking at the study of genetic material and trying to answer a question running through the corridors of research. in genetics. What is the substance that transmits hereditary traits between generations? Are they proteins or nucleic acids? When he heard Wilkins lecture and saw the X-ray images of DNA, James Watson (1928) wrote: DNA Study”.

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In late 1951, he joined Imperial College London as a strong-willed young researcher, particularly adept at using X-rays to study the chemical composition of matter. The British Rosalind Elsie Franklin (1920-1958) came from the National Center for Scientific Research in Paris, where she worked on the study of the chemical composition of coal by X-ray diffraction imaging of its crystals, and she became one of the most brilliant researchers in this field.

Randall, the director of the biochemistry laboratories at Imperial College, instructed him to apply this method to studying DNA rather than studying proteins. Rosalind used the advanced imaging tools Wilkins had requested and the DNA preparations sent to them by Professor Sayner in Switzerland, and researcher Gosling moved into the lab to continue his doctoral thesis with her. He continued his work on DNA imaging as an Imperial, while Wilkins believed the project was still up to him. Principal Randall’s unclear duties lead to a rift between Wilkins and Rosalind.

Photo 51:

Gosling completed the preparation of the DNA sample, set up the imaging tools and the special film used in it, and then took X-ray diffraction pictures of the molecules of this strange substance. He was preparing his PhD thesis in physics under the guidance of researcher Rosalind Franklin at Imperial College London. It was a beautiful spring day in London in March 1952. After many hours of waiting, which he spent in photography and development, the new image appeared, and as soon as Gosling saw it, he knew it was the clearest image and named it “Photo 51”.

Figure 51 of DNA obtained by Raymond Gosling and Rosalind Franklin at Imperial College London in March 1952, showing the regular helical shape of this DNA structure. This picture was the main reason for knowing the chemical composition of DNA

Rosalind Franklin gave a lecture in November 1951 on the results of her research and her understanding of the chemical structure of DNA. Watson, a young researcher, was in the audience, but he did not realize at the time the importance of his research and the significance of the images he showed, but it sparked his curiosity to study the structure of DNA and try to create a model of it. chemical structure.

Watson, along with his colleague Crick at Cambridge University, made a model of this DNA in late 1951, as they were imagining its chemical composition at the time, and that model was in the form of a triple helix. Some researchers from Imperial College were invited to see the model, Rosalind Franklin. But upon seeing the model, he burst out laughing and sarcastically said that this model cannot be correct and is not compatible with the studies, information and X-ray images of this acid.

Rosalind’s directness, her habit of looking directly into the eyes of those with whom she spoke, and her short and direct manner of speaking caused feelings of resentment and uneasiness among those around her. Perhaps it is also because she is a strong woman in the then male-dominated world of physics, chemistry and biology research and laboratories.

Rosalind Elsie Franklin (1920-1958) Her research on X-ray diffraction imaging helped lead to the chemical structure of DNA

Although researchers at Imperial College London’s laboratories pioneered the simplest picture of DNA’s chemical structure, they were not the first to learn the details of that structure, perhaps because of personal differences between them. because of the ill-advised administrative decisions of John Randall, the director of the laboratory, or the sharp personality of Rosalind Franklin, versus the shyness and isolation narrated by Maurice Wilkins.

The point is that Rosalind asked to be transferred to the Graduate School of Research at Birkbeck College of the University of London, Randall accepted her resignation and asked that all the results of the nucleic acid study be handed over to the Imperial College laboratory. . As for winning the race to discover the chemical structure of DNA, it was the luck of two young researchers at the University of Cambridge, Francis Crick and James Watson.


Dr. Amer Sheikhoni’s book “The History of Heritage as Discovered by Its People”.

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