school energy&environment

A “silent” scientific revolution

More than half a century ago, on 25 April 1953, a short article just 900 words long, appeared on the scientific magazine Nature. It dealt with the discovery of the double helix structure of the DNA molecule, a molecule that contains genetic information and has a three-dimensional conformation. We will see why the latter is recognized today as a fundamental scientific discovery, but first let us get to know the history of ‘our scientists’ better and the scientific milieu they worked in. The authors of the article were James Watson e Francis Crick: two young and ingenious English researchers who worked together in a laboratory of the prestigious university of Cambridge. J. Watson was 24 years old and was a vivacious and talented youngster, F. Crick was 36 years old and had worked as a physicist in the university. The discovery of the three-dimensional nature of the DNA molecule took place in February, two months before it was published publicly; at the moment, however, it did not draw great interest on the part of the scientific community of biochemists. Apparently it was not considered fundamental since not much importance was given to DNA yet. Many scientists of the Fifties believed that the DNA molecule was only an accessory respect to the mechanism of life but that proteins played a fundamental role. As a matter of fact, only later it was discovered that genetic information is contained and transmitted thanks to DNA that allows proteins to be built up and that proteins do not contain information to make other proteins. Hence at the beginning only a few researchers of J. Watson and F. Crick’s working environment understood and enriched the epoch-making discovery that the two scientists had revealed in just one page with a photograph.  Indeed even the revolutionary article seemed to have had a very ‘domestic’ beginning. Odile, Crick’s wife, built the famous three-dimensional DNA model, made up of balls and sticks that appeared in the photograph along with the two researchers observing it; Watson’s younger sister, Elizabeth, instead, gave up a relaxing Saturday afternoon to type out the 900 words dictated by the two scientists to send to Nature.
J. Watson and F. Crick were the first to reveal the spatial structure of DNA thanks to an intuitive and fruitful reading and re-elaboration of many studies carried out earlier by various scientists, and indirectly thanks to another researcher who, in parallel, had managed to photograph the DNA structure with X-rays. This fundamental photograph, taken by Rosalind Franklin, was shown to them by a professor without her knowing. J. Watson e F. Crick analysed the picture and perceived what Franklin had failed to assume, i.e. that the DNA molecule has a three-dimensional structure. Years later, this discovery proved to be the most important brainwave in the field of Life Science of the last 50 years, since from then on  it was possible to understand how genetic transmission from one generation to the next works.
Today it is possible to define the structure of DNA as a double helix made up of two intertwined filaments like the newels of a winding staircase whose rungs are made up of molecules of hydrogen that bind the nucleotides. What are nucleotides? They are the basic building blocks of DNA, each one is composed of a molecule of phosphoric acid, a sugar called deoxyribose and a nitrogen base. The nitrogen bases are of four different kinds: adenine (A), guanine (G), thymine (T) and cytosine (C). The pairing of the nitrogen bases that make up DNA follow a precise principle. In the Fifties all this had not been understood and explained yet, so let us see how what we know today was discovered, by getting to know the scientists and the various stages of their research.