Science: DNA, 50 years on

It is exactly 50 years since one of the greatest scientific breakthroughs of the twentieth century – the working out of the structure of the DNA molecule . This represented the culmination of fifty years research in the fields of physics, chemistry and biology, a milestone on the road started by Darwin’s ‘Origin of Species’ a century before. From this discovery spring immense possibilities in the understanding of life itself and the treatment of human diseases, but also immense dangers. How did this breakthrough come about and what did it consist of?

After World War II, techniques of physics developed in the previous thirty years were focused on biological matter – often by physicists disgusted by the use of their work to make weapons of mass destruction. By the 1940s it had been possible to work out the way in which atoms fitted together in simple crystals such as common salt. But the job was difficult and, in the age before computers, took a very long time. Biological processes involved molecules with hundreds of thousands of atoms linked together and working out their structure seemed almost impossible. It was important because if the structure of molecules such as insulin could be worked out, it would be easier to make synthetic versions. But working out the structure of the components of living cells was an even greater challenge.

Chromosomes and genetics.

For many years biologists worried about the way in which plant and animal characteristics were passed from one generation to another. In the nineteenth century, Charles Darwin and Alfred Russell Wallace rocked the scientific world with the theory of evolution. At the same time Mendel studied the transfer of characteristics between generations of pea plants and came to the conclusion that each plant carried a collection of blocks of information from each parent but that some blocks were ‘dominant’ and some ‘recessive’ – accounting for variations from one generation to the next. But the actual mechanism for this transfer was only discovered when biologists were able to make detailed studies of cells – the ‘atoms’ which make up living things. They found that each cell has a nucleus which contains pairs of threadlike structures – chromosomes. In the human cell there are 23 such pairs. One of each pair comes from the father and one from the mother and they carry the information on the physical characteristics of each parent. Each chromosome therefore could be thought of as a string of ‘genes’ each one of which carries some genetic information (for example hair colour). But the form and chemical composition of these ‘genes’ was unknown.


By the middle of the last century it became clear that the basic material which made up these chromosomes was the deoxyribonucleic acid (DNA) molecule. But the actual form and structure of DNA was unknown – how it was able to ‘code’ genetic information and how that information could be passed on. A combination of inspired guesswork and brilliant experimental technique (see box) enabled the famous ‘double helix’ structure for the DNA molecule to be worked out in 1953. It was found that the two helices were linked like steps in a spiral staircase and each of these links carried genetic information. So the actual building blocks of life could be observed and studied. From being a theoretical idea to explain the passing on of characteristics from parents to offspring, genes could be isolated, studied and, in theory, modified.

The Doctrine of DNA

In principle, the whole genetic map of any living thing can be mapped out. But the total amount of genetic information carried by a human’s 23 chromosomes has three thousand million elements. Only because of the fantastic development of computing power and experimental technique has it been possible to consider carrying out such a project. In 1990 the ‘Human Genome Project’ was set up, expending billions of dollars on that very job. Now, half a century after the unravelling of the structure of the DNA molecule, it has become possible to work out the actual structure of human DNA and the ‘final’ map will be published to mark the 50th anniversary of the discovery of DNA structure.

What does that map actually show? Not as much as might be expected; a collection of pieces from a large number of individuals studied in different laboratories, it give a map of the genes of an ‘average’ human being. A very few areas on the map have been shown to be responsible for some genetically transmitted diseases, but most have unknown functions. But the project itself has helped to resurrect the ancient, discredited and profoundly reactionary doctrine of genetic determinism. In this view, every characteristic of an individual is encoded in their genome. One senior biochemist stated that given a large enough computer and the complete DNA sequence of an organism he could totally describe its anatomy, physiology and behaviour. Or, to put it the other way round, if a person is poor, uneducated and unemployed the reason lies in their genetic makeup not in the social system.

When Daniel Koshland, editor of the US magazine Science was asked whether some of the billions spent on the ‘Human Genome Project’ would not be better spent on the poor, he exploded "What these people don’t realise is that the homeless are impaired….no group would benefit more from the application of human genetics" – by which we can only infer that the ‘impaired’ or ‘subhuman’ homeless would be quietly eliminated. Perhaps such determinists believe in the existence of a ‘homelessness’ gene which could be tested for before birth. Any foetuses carrying the gene would be aborted – a modern version of the Nazi eugenics programme.

Of course, this is as much scientific nonsense as Hitler’s theories. No-one would deny that physical characteristics such as skin or hair colour are transmitted genetically. But even such simple characteristics are developed or modified by the individual’s social environment (e.g. David Beckham’s hair). The list of three billion elements in my DNA may point to some potential developments and away from others but these are only potentials not certainties. And even then, it is impossible at the moment and probably in the future to identify which genes or groups of genes affect other genes to produce particular results. The only truth is in Engels’ words ‘social being determines consciousness’.

The false doctrine of biological determinism (sociobiology or evolutionary psychology to give two other names under which it lurks) can be used to justify the status quo in society – a modern spin on the old hymn ‘The rich man in his castle, the poor man at the gate. God made them high and lowly and ordered their estate’. Socialists know that no god and no packet of genes makes inevitable the waste and degradation of the capitalist system.

The working out of the structure of the DNA molecule was a scientific milestone. But like any other scientific discovery, the use to which it is put depends completely on the social system in which it exists. In capitalist society, where such research is in the hands of the huge biotechnology companies, its use is at best to make those companies richer. At worst it is another method of social control.


The science of chemistry developed an understanding of complex molecules made up of combinations of elementary atoms (for example water H20 – two atoms of Hydrogen linked to one Oxygen atom).

But chemical processes only gave indirect evidence of the actual shape of such molecules. By the 1930s it was possible to study some molecules directly by the technique of X-ray diffraction. X-rays are radiation like light but with much shorter wavelengths, wavelengths small compared with the size of the atoms that make up molecules. So shining a beam of X-rays on a pure specimen of a substance produces a diffraction pattern in the same way that light is scattered when it is reflected from a surface with a very fine-grain structure like a compact disc. In either case, it is possible to work back from the pattern to give the shape of the diffracting structure that produced it. But any complex molecule produces a fiendishly confusing pattern.

So working out the structure of a complex molecule requires two steps: first the production of pure samples containing thousands of the molecules and taking a clear and unambiguous picture of the X ray diffraction produced. Second, using that pattern to work back to the molecule producing it – usually by guessing at the shape of the molecule and calculating the pattern such a shape would give.

This was the task tackled in 1952-3 by two research groups, one in Cambridge , one in Kings College London. In London Rosalind Franklin produced the best existing X ray patterns from DNA. Without her knowledge, her boss Maurice Wilkins passed the pictures on to two Cambridge researchers James Watson and Francis Crick. The pictures were all they required to firm up a guess Watson had made earlier on the structure of the molecule. They went ahead and published their results. without giving due acknowledgement to Franklin.

Franklin died in 1958. In 1962 Watson, Crick and Wilkins received Nobel prizes for their discovery. Wilkins and Crick remained in academic research. Watson became a big wheel in the world of biotechnology and a strong proponent of genetic determinism and the idea of a genetically determined underclass.

Medical uses.

What have been the positive gains from the unravelling of DNA? First and most important, some genes have been identified as responsible for particular inherited diseases. The most famous and heartening case involved a child who had inherited a defective gene which stopped his immune system working, leaving him in mortal danger from the most innocuous diseases. He was cured by a blood transfusion containing his own cells which had been genetically modified.

But many other cases are much more problematic. For instance a defective gene which can cause breast cancer has been identified. So women can be screened for this gene. But when a genetic test has shown a predisposition to a disease, do insurers or employers have the right to discriminate against people on this basis? And should parents be able to ‘screen’ eggs and sperm to deliver only children in the model they require?

The clearest common example of DNA testing is matching up DNA ‘fingerprints’ either to establish relationships between people (e.g. paternity of child) or to establish the presence of an accused at a crime. But even there controversies arise. In court, it is easy for a prosecution lawyer to stand up and declaim some astronomical figure for the odds against the accused. Quite possibly the result is not so clear cut. There have already been some ‘anomalous’ positive matches for people who could not possibly have been involved in a crime – leaving aside the horrific situation in Texas where 32 people have been executed on DNA evidence now admitted to be faulty.

The best known example of genetic modification is the battle over GM food. Introduced by the big agrochemical monopolies, supporters claim GM as the answer to everything from world starvation to environmental pollution. They try to smear opponents as cranks and reactionaries. In fact many of the problems which GM food is supposed to cure were produced by the agrochemical business itself. And opposition in the most part reflects a healthy scepticism of ‘trust me I’m a scientist’ pronouncements by spokespeople paid by big business.

The unravelling of the mysteries of genetic coding can be a huge gain for humanity. But they will only be an unadulterated benefit if their development is taken out of the hands of the big pharmaceutical and agribusiness monopolies.

This is a longer version of an article that was first published in The Socialist, paper of the Socialist Party, CWI, England and Wales.

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April 2003