Under The Microscope

THE DOCTRINE OF DNA: BIOLOGY AS IDEOLOGY by R.C. Lewontin; Penguin Books, 1994; 130 pages; $24.95

Reviewed by Craig Webster

If you are looking for a clear and critical overview of modern genetics research, one which cuts through all the hype and misinformation, then read this book. Lewontin, a Harvard University geneticist, has collated six of his radio lectures given to increase public understanding of what research programmes like the Human Genome Project really mean.

The Genome Project is a vast undertaking which aims to map every single gene in the human body. The basic idea is that once a gene for a specific disorder is identified an accurate blood test can be developed to detect it. An individual with that disorder can then be cured by undergoing gene-replacement therapy to "overwrite" the defective gene with a properly functioning one.

Claims, even by the experts, about what this will mean for humanity have been superlative, to say the least. Medicine will essentially cease to exist since it will be far better to fix the gene causing a disorder than to prescribe drugs for it. Currently incurable diseases such as cancer, Alzheimer's, Huntington's and almost any other you care to name will become curable. Cosmetic gene-replacement therapy for poor eyesight, hearing loss and baldness are possible, and even social problems such as violent crime, alcoholism and anti-social behaviour can be treated just as soon as we localise the relevant genes -- or so the story goes.

Lewontin dispels two myths central to the Project and the gene-replacement paradigm. First the relationship between genes and disease is just not that simple, and second, there is no evidence whatever that every human ill has a corresponding gene or set of genes. While our genes certainly guide our development, we are not perfectly determined by them. For example, the fingerprints on your left and right hands are not identical, yet their development is controlled by the very same genes. The variability is produced by "developmental noise" at the cellular level during growth. It is therefore impossible to say that one particular set of fingerprints is precisely determined by one particular set of genes. Add to this environmental influences and the developmental story becomes even more complex.

The idea that every human disease must have a corresponding gene is plain fancy according to Lewontin, especially when you start to consider the complex ills of societies rather than the disorders of individuals. Certainly some disorders are more genetically determined than others. Huntington's disease, for example, seems to be strongly genetically determined, and so is well suited to a gene-replacement approach. But many, perhaps most, human diseases will not have identifiable genetic determinants. Even when gene-replacement is possible there are risks. For example, if you have part of your DNA overwritten these changes maybe passed on to your children and nothing is known about the risks involved in inheriting altered genes.

The potential of the project to better our lives is substantial, but it is certainly no panacea. We must be aware of the risks and limitations as well as the benefits of any new technology, especially one which acts directly on the genes which make us all who we are.

Craig Webster is currently a clinical researcher in the Anaesthetics Department at Auckland's Green Lane Hospital.