Although there were many individuals involved in the race for the double helix, this unit will focus on just a few of the key players directly involved in this discovery. The majority of the information presented in this history section came from my favorite source, The Eighth Day of Creation (#10) and from The Double Helix (#2).
-Erwin Chargaff-
American biochemist, working in New York at Columbia University
-Francis Crick-
English physicist, working in Cambridge at Cavendish Laboratory
-James Watson -
American biologist, working in Cambridge at Cavendish Laboratory
-Rosalind Franklin-
English chemist/crystallographer, working in London at King's College
-Maurice Wilkins-
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English chemist/crystallographer, working in London at King's College
-Linus Pauling-
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American Professor of Chemistry, working at CA Institute of Technology
Our story begins in 1950 when young James Watson journeyed to England to pursue research there. He was only twenty three when he left America, just after he earned his Ph. D. He knew phages (viruses that attack bacteria) and intended to continue his post-doctoral research in this area at the Cavendish Laboratory.
When Watson arrived in England, he met Francis Crick, a man in his early thirties pursuing his post-doctoral work. Crick was interested in proteins, and their structure, and he used a technique called x-ray crystallography to study proteins. Crick was reported to be very knowledgeable due to his voracious appetite for reading.
Upon meeting, the two quickly developed a sincere working relationship. They were able to compliment each other’s research- Watson’s background in biology was nicely balanced by Crick’s background in physics. Neither were involved with DNA research when they met, and they never actually did any research directly with this molecule even though they are credited with the discovery of its structure.
At this point in time, the research showed that the genetic material was DNA, yet no one knew about the structure of this molecule. What was known was something called “Chargaff’s Rules” which resulted from Chargaff’s study of DNA from many different species. What he discovered was a ratio of nitrogenous bases. He noted that there were always approximately equal proportions of adenines to thymines as well as guanines to cytosines. It took some time before anyone realized the significance of this.
Many teams were interested in being the first to determine the structure of the DNA molecule. Linus Pauling proposed that it was a three chained helix, yet he never really did much research with DNA since he was already deeply involved in other areas of research. At this time he had a successful background in helical proteins. Many teams around the world were interested and involved with DNA, yet for our purposes we will note Maurice Wilkins and his team and King’s College as the team that was most actively pursuing research in this area.
A new member joined Maurice Wilkins at King’s College in 1951, Rosalind Franklin. She was under the assumption that she was given the DNA work upon her arrival to the King’s College laboratory. She was the one to clean off the dusty files and equipment in order to perfect the technique of x-ray photographing a DNA molecule.
With so many individuals working with DNA in Europe, eventually Watson and Crick also became interested in this DNA molecule enigma. In fact, the two were eventually asked to back off since Wilkins’ team had ‘first dibs’.
For quite some time it was not clear if DNA was a helix, and if it was, how many strands it was composed of. Rosalind Franklin produced some fabulous x-ray photographs, yet even she did not realize how her photographs showed that DNA was a double helix. It took the ingenuity of the Watson-Crick team to make this clear.
Before Crick even saw these x-ray photographs, he heard about them from Watson. Watson attended a seminar where Rosalind Franklin presented her discoveries. She showed her photographs to the seminar attendees, and described other aspects of her DNA research. Watson returned to Crick’s surprise without any notes from the seminar. Watson trusted his memory, but it failed him because he was only able to relate to his partner qualitative descriptions rather then exact quantitative descriptions. Some feel that if Crick attended the seminar, or if Watson took notes, they may have solved the puzzle sooner.
Crick’s experience with x-ray diffraction by helical proteins made it much easier for him to decipher the information in the x-ray photograph of a DNA molecule. He was able to make mathematical calculations about bond angles and distance between atoms. Yet his initial calculations were off, even if only slightly and then he and Watson were asked by their cooperating supervisor to lay off DNA and get back to the work he had intended for them. And they did for about a year.
According to Judson, Rosalind Franklin was probably the only person still working with DNA during 1952. During this time she produced more and more photographs; yet she was still not ready to put faith in the idea of a helix. She kept detailed lab notes, and on several occasions she noted to herself that she did think that it could be a helix, or a double helix, yet she was cautious and conservative and kept these thoughts between herself and her notebook. In public she scrutinized the idea of it being a double helix. Some believe that she did not have the experience nor foresight that is required for pulling any and all data about structure from the x-ray crystallography photographs.
Maurice Wilkins initially gave Rosalind Franklin the green light to put all her efforts into DNA. When he requested that she share her findings, she put up the red light. She did not assume that this was a joint project, she believed it was hers. She and her research assistant worked diligently, perfecting the technique of isolating single fibers for x-ray crystallography and in doing so produced over 50 photographs of DNA in both its B and Z forms (Which by the way led to part of the reason Rosalind Franklin was not quick to adopt the double helix theory- the two structures gave two different photographs and it was yet to be known for sure that there were two forms of DNA.) This misunderstanding between Franklin and Wilkins quickly became a source of animosity.
Ultimately Watson and Crick resumed their quest and reentered the race. This time Crick actually saw the photographs taken by Franklin. Within weeks they were building models, trying to find a structure that conformed to the measurements Crick calculated from the x-ray photograph data. Within days, they found success- they figured it out!
In April 1953, Watson and Crick published their 2-page paper entitled: “Molecular Structure of Nucleic Acids: A Structure for Deoxynucleic Acids.” The world was shocked, and they were too. The two made history, not only for discovering the structure of a DNA molecule, but also as two scientists who, although both extremely clever, won the race riding on the backs of others.
A Nobel Prize in Medicine or Physiology was awarded in December 1962 to Watson and Crick for the discovery of the DNA structure and to Maurice Wilkins for the x-ray photograph. Even though it was Rosalind Franklin who took the photograph, she died of cancer in 1958 year at age 37. I do not think it is presumptuous to assume that her developing cancer was directly job related, basing this on what we now know about exposure to x-rays and their link to mutations. It doesn’t seem fair that Nobel Prize Laureates must be alive when presented the award. When you consider the relationship between and the situation with Franklin and Wilkins, one can clearly see an injustice to Franklin since it was her diligence and perseverance that produced the photographs.
