Discovery of the chemical structure of DNA

As medical research moves to an increasingly cellular and genetic level, the importance of understanding and manipulating DNA is becoming more apparent in healthcare.

Deoxyribonucleic acid, to give it its full name, is a nucleic acid divided into segments called genes that contain the genetic instructions for every individual.

Its prominence has come to light over the past 50 years, allowing for improved disease diagnosis, the ability to detect a person's genetic predisposition to certain diseases and the creation of new drugs, in particular in the field of HIV/AIDS.

Gene therapy treatments have also been developed, and there is increasing research into custom designed drugs based on an individual's genetic profile.

Although first isolated in 1869 by Swiss scientist Friedrich Miescher, it was not until the middle of the 20th century that its true potential began to be realised when its structure was discovered by two Cambridge University biologists.

On February 28, 1953, James Watson and Francis Crick determined that DNA was a double-helix polymer – a spiral of two DNA strands wound around each other.

Each stand contains a chain of nucleotide monomers, which allow organisms to transfer genetic information from one generation to the next.

The discovery proved to be one of the most important scientific advances of the 20th century. It was a thought acknowledged by the two men, with Watson writing in his book, 'The Double Helix', that Crick announced their breakthrough in Cambridge pub, the Eagle, declaring: “We had found the secret of life”.

The work of Crick and Watson went on to be published in Nature magazine on April 25, 1953, in an article entitled 'A Structure for Deoxyribose Nucleic Acid'.

The paper was a turning point in scientific thought, striking a blow to the Vitalist thought camp of biology, that saw genetics as too complex to understand fully, by demonstrating how deciphering such a process was entirely possible.

Crick and Watson also commented on previous efforts into the structure of DNA from the California Institute of Technology's Linus Pauling in their paper.

Pauling had been researching DNA structures at the same time as Crick and Watson, becoming the first scientist to discover that certain proteins can have a helix shape in 1951.

His proposed model for DNA, of a three-stranded helix with the bases facing out, that he sent to be published before Crick and Watson's paper, was incorrect, however, with the two describing such a structure as 'unsatisfactory'.

Things could have been very different, though, if Pauling had been able to see an X-ray photo of DNA taken by Rosalind Franklin and Maurice Wilkins of King's College, London, which provided the necessary evidence for Crick and Watson's double helix shape.

However, Pauling had been denied his request to see the photo in 1952, and was not given a chance to make his appeal to Wilkins and Franklin in person as the US government barred him from travelling because of his anti-war activism during World War II. 

Pauling did go on to win the Nobel Prize in Chemistry in 1954, though, for his research into the nature of the chemical bond, and was awarded the Nobel Peace Prize in 1962 for his campaigning against nuclear tests and the spread of arms.

This was also the year Crick and Watson picked up their Nobel Prize in Physiology or Medicine, shared with Wilkins. At the time, the Nobel organisation only honoured living recipients, which meant that Franklin, who had died of ovarian cancer in 1958, was not eligible.

Her work, and that of her colleagues, remains among science and medicine's greatest achievements, with investigations constantly ongoing into how, through understanding and altering DNA, someone's health can be improved.

The results can be seen in such developments as recombinant DNA - the process of removing DNA from one organism and inserting it into the DNA of another organism - in medicine, which can be used to develop drugs, vaccines, and to reproduce important human hormones and proteins, such as insulin.

And much has been made of using genetic data to give patients 'personalised' treatments, leading to more accurate drug prescriptions and greater awareness of potential adverse events.

The structure and behaviour of DNA may have now been decoded, with its benefits showing 60 years later. Full understanding of its applications still has some way to go, however, with genetic diseases and infectious diseases, the immune system and cancer all targets.

The author
Tom Meek, web editor at PMLiVE