The most famous image to emerge from 20th-century biology is the deoxyribonucleic acid (DNA) double helix, illustrating the structure of the gene, life’s genetic material.
Credit for the discovery of the double helix is popularly accorded almost entirely to James Watson and Francis Crick, both now immortalised in the pantheon of all-time scientific heroes.
But the sole experimental evidence on which the double helix structure is based is an X-ray diffraction picture of DNA (Photograph 51) taken by PhD student Raymond Gosling working under crystallographer Rosalind Franklin’s supervision at King’s College London. This picture is the scaffold that supports the double helix. But Franklin’s contribution to discovering the double helix rarely receives more mention than a footnote.
Rosalind Franklin was born in 1920 into an affluent and influential British Jewish family. She remained culturally Jewish all her life, although religiously she was agnostic. She distinguished herself academically at a young age. She was also very athletic, greatly enjoying hillwalking and mountaineering throughout her all-too-short life.
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Franklin went on to Cambridge University and graduated in physical chemistry in 1941. She was awarded a PhD in 1945 for her studies on the structure of coal and graphite.
Franklin began postdoctoral studies in 1947 in Paris, where she perfected the technique of taking X-ray diffraction photographs. She moved to a position at King’s College London in 1950 to study the structure of DNA. Two separate teams worked on DNA structure at King’s College, one led by Franklin and the other by Maurice Wilkins. Franklin and Wilkins clashed temperamentally.
Franklin supervised Gosling’s research initially, and during this period, he took that famous and beautiful X-ray diffraction photograph (Photograph 51) of DNA. He later moved under the supervision of Wilkins.
Solving the structure of DNA was the most important problem in biology at the time and three main groups were in the race. One was led by the great American chemist Linus Pauling. James Watson and Francis Crick were working on the problem in the Cavendish Laboratories at Cambridge and Franklin and Wilkins in King’s College. Initially, the smart money was on Pauling, already a Nobel laureate (1954) for chemical-bond research, to win the race.
One day while this work was going on, Watson visited Maurice Wilkins at King’s College, where Wilkins showed him Photograph 51. Wilkins didn’t inform Franklin of this at the time.
Watson later recalled that when he saw the photograph, “my jaw fell open and my pulse began to race”. The photograph convinced him that the DNA molecule was a helix.
He rushed back to Cambridge, where he and Crick were building models of DNA and they began fitting cardboard cut-outs of the four types of nucleotides found in DNA into double helical structures.
They solved the riddle relatively quickly, announcing their double helix discovery in Nature in 1953. Watson, Crick and Wilkins were jointly awarded the 1962 Nobel Prize in Physiology or Medicine for this work.
Franklin moved to Birkbeck College London in March 1953, recruited by physics department chairman John Desmond Bernal, a noted crystallographer, proselytising communist and an Irish man, born and raised in Co Tipperary.
Franklin began work on RNA, an equally central molecule to life as DNA, and to study the structure of tobacco mosaic virus (TMV), an RNA virus. She elucidated the structure of TMV and pioneered the field of structural virology.
She died of ovarian cancer in 1958, a condition possibly caused by exposure to X-rays. The early crystallographers were unaware of the health dangers of exposure to X-rays.
It is often remarked that Franklin had an awkward personality and was difficult to work with. She spoke directly and concisely, looking into one’s eyes.
This particularly unsettled Wilkins, who was shy and circumspect in his conversation. On the other hand, Franklin‘s friends have paid tribute to her warmth and loyal friendship.
Bernal wrote: “As a scientist Miss Franklin was distinguished by extreme clarity and perfection in everything she undertook. Her photographs are among the most beautiful X-ray photographs of any substance ever taken. At the same time, she proved to be an admirable director of a research team and inspired those who worked with her to reach the same high standards.”
History has treated Franklin unfairly and an honest reappraisal and acknowledgment of her DNA work is long overdue.
- William Reville is an emeritus professor of biochemistry at UCC
