James Watson, Francis Crick, Maurice Wilkins and Rosalind Franklin

In the middle of the 20th century, two young men whose names would become synonymous with DNA arrived at the University of Cambridge. British-born Francis Crick (1916 - ) had a strong background in physics. But Crick was fascinated by biology and decided to switch fields. In 1949, he became a graduate student in molecular biology at Cambridge. Crick’s friend James Watson (1928 - ) was an American from Chicago with a passion for bird-watching. In 1950, Watson left Indiana University with a PhD in zoology and an interest in genetics. The next year, he went to a symposium in Italy, saw his first x-ray study of DNA and met biophysicist Maurice Wilkins (1916- ). Fascinated, Watson decided to study protein and nucleic acid structure. He ended up at Cambridge, where he and Crick spent long hours puzzling over the structure of DNA. Using experimental evidence from other scientists, they built model after model – first, out of cardboard, then from metal plates and brass rods.

At nearby King’s College in London, an ambitious young woman named Rosalind Franklin (1920-1958) was also trying to figure out DNA. Franklin was an expert in x-ray crystallography, the use of x-ray photographs to determine the structure of a molecule. By the time she was 26, the British scientist had earned a PhD in physical chemistry from Cambridge University and published five papers. In 1951, Franklin came to King’s College. But friction soon developed between Franklin and her colleague Maurice Wilkins. Wilkins was a senior researcher with a physics PhD from Birmingham University. He worked on a variety of projects involving DNA. When Franklin arrived at the laboratory, Wilkins was away. A misunderstanding over Franklin’s position – Wilkins thought Franklin had been appointed as his assistant – and personality differences contributed to an uneasy relationship.

Watson and Crick used Wilkins’ x-ray studies of DNA to help them build their models. But it was Rosalind Franklin who unwittingly gave them their final clues. With her x-ray photographs, Franklin learned that DNA can exist in two different forms. From this, she knew that the phosphate groups must be on the outside. She also discovered that one of the two forms looked very much like a helix. But, to Wilkins’ frustration, Franklin wouldn’t agree that DNA was a helix until she was sure about both forms. Without asking her permission, the exasperated Wilkins showed Watson and Crick one of her excellent x-ray photographs. This clear picture of a helix was the final clue they needed. With a leap of insight, Watson and Crick realized that DNA must contain two chains of nucleotides going in opposite directions, with the bases in the middle. In1953, Watson and Crick published their discovery.

It wasn’t long before Franklin, Wilkins and others demonstrated experimentally that Watson and Crick’s model was correct. In 1962, Watson, Crick and Wilkins shared the Nobel Prize in Physiology or Medicine. But the Nobel Prize can only be given to scientists who are still living. Franklin, who died of cancer four years before, could not share the honor.




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