Thursday, 28 February 2013

60 Years Ago on This Day: The DNA Structure's Discovery

On the 28 February 1953, James Watson and Francis Crick pieced together the first model of a DNA molecule – the three-dimensional double helix. A brilliant insight and also an interesting story that lifts the lid on the less appealing side of a scientist’s life – the race to beat your fellow scientists to the Nobel prize even at the cost of 'spying' (to use Watson's own word) on competing scientists. There is the notorious episode in which Watson peeked at Rosalind Franklin's X-Ray Crystallography image of DNA without her knowledge and consent. The fact that she died a few years later, apparently without knowing what massive contribution she had made to the the DNA structure's discovery, makes for a rather sad story.

It was perhaps the unfairness of this episode that prompted some commentators to ask quite how much Crick and Watson’s breakthrough owed to other scientists. Watson himself acknowledged without hesitation that they could not have succeeded without Franklin's involuntary help. There was one other contemporary scientist who supplied an important piece of the puzzle Crick and Watson so brilliantly solved. In 1950, Erwin Chargaff discovered a remarkable symmetry in the amount of nucleotides -  regardless of the species the DNA came from, Adenine occurs in equal amounts to Thymine, and Cytosine occurs in equal amounts to Guanine. Based on this, Crick and Watson figured out how the nucleotides were paired up in the DNA molecule.

Going further back in time, the first clues as to the structure of DNA was provided by Phoebus Levene in 1919. He revealed for the first time the polynucleotide structure of DNA. He also discovered ribose and deoxyribose as well as identifying sugars and phosphates as chemical constituents of the DNA molecule.

As for the function of DNA, this was well known by the time Crick and Watson elicited the structure of the molecule, although it wasn't clear how that function was performed. It was as early as 1869 when Johann Friedrich Miescher stumbled over DNA  (he called it “nuclein”), while studying the proteins in white blood cells. Amazingly, he even had the hunch that nuclein was the agent of heredity – an idea that was so far ahead its time that it didn't attract much notice. Decades later, in 1904 Thomas Hunt Morgan proved the correlation between chromosomes and hereditary traits, famously experimenting on fruit flies.  And in 1944 Oswald Avery proved that DNA was the active agent in heredity.

Crick and Watson’s breakthrough was indeed made possible by the work of many other scientists (everything considered, probably many more then the ones mentioned above). It is usually like that - hardly any scientific theory comes out of the blue, especially in our day and age when human knowledge is becoming more and more complex. The fact remains that the two scientists were the first to discover the structure of the DNA molecule and they deserve their prize. Had Rosalind Franklin lived, she would have certainly shared in the 1962 Nobel prize, as did her colleague at King's College London, Maurice Wilkins. I remember a happy note in Channel 4's "DNA - The Story of Live": Those who knew Franklin well say that what she wanted most was for her work to contribute to scientific advancement. That it most certainly did.

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