Steve Jones - The Language of the Genes

Such calculations sound offensive, or even brutal, but equations like these are commonplace in medicine. To balance cash against quality and length of life is unavoidable; and the sums may be stark. Even so, given that so many single-gene conditions cannot be treated and that many of the others demand permanent care, they are relatively simple to cost. At first sight, and forgetting any moral dimension, the equations seem clear, both for pre-natal diagnosis and for the care of those born with an inherited illness. For genetics, though, costs and benefits have ambiguities of their own. Now that DNA has entered the domain of common diseases it will allow early diagnosis of conditions, treatable and not, that come on in later years. As it does so it may produce a whole new social class, the healthy ill, who — hale and hearty as they are until the fate coded into their genes makes its presence felt — turn to doctors for help that they cannot give.

The biggest difficulty may prove to be diagnosis by proxy, the inadvertent discovery that a third party, a relative, is at risk. Should doctors inform other family members, even those outside their own care, of their situ- ation? Already physicians have been sued for not telling relatives of a death from inherited colon cancer because the information might have allowed them to protect themselves. In the USA some states see doctors as responsible for informing the wife of a psychopath of her own risk and insist that physicians must tell the rest of the family about inherited disease. Others feel that to inform the patient is enough and leave it to him what he does (the practice recommended by a British Select Committee). Most people, when asked, agree that relatives should be told about inborn conditions and this may become common practice — which changes the normal taws of confidentiality. And how long must a hospital keep in contact with a patient? As more accurate tests emerge, as they will, those who once scored negative on a DNA checkup might then not do so.

Genetics hence calls for decisions about what information should be gathered, by whom, and to whom it should be available. It shifts the boundary between private and public responsibility. To what extent do duties extend within a family? Where do medical decisions end and the values of society take over? Fortunately, perhaps, the more we learn, the more unlikely the notion of a universal screen for imperfection appears.

Without doubt, genetic tests may be helpful. To terminate a pregnancy can be a great relief to a woman found to be carrying a damaged foetus. On a more positive note, any parent with a child with phenylketonuria or inherited colon cancer (each of which can be treated) knows how important genetic checks can be. Perhaps screens of whole populations will find many of tomorrow's patients. They could identify those at particular risk, be they for smoking, stress, chemicals, or certain foods. The new insight into how DNA interacts with the world outside may at least change attitudes to risk. Most people know that to smoke causes cancer and that a fatty diet may lead to heart disease. Certain genes predispose their carriers to the harmful effects of tobacco or rat and some individuals may be able to drink, smoke or eat lard with impunity. Propaganda about smoking and lung cancer has not been very effective. Those exposed to it have an impressive capacity to assume that if one smoker in ten contracts rhe disease, then that will be someone else. If it is possible to identify exactly who will get cancer if they smoke, individual terror may prove a better deterrent than collective risk. One form of the gene for a protein called alpha-i anrrypsin much increases the risk of emphysema among smokers. The incidence of those with two copies is around one in five thousand; and half of all smokers unlucky enough to fall into that group die younger than forty, whereas the lifespan for gene carriers who do not smoke is extended by twenty years. To discover one's individual danger concentrates the mind: and in Sweden one in ten teenagers with the high-risk genotype smokes, compares to a fifth of others.

To assess future health is not new. All doctors check their patients for high blood pressure and healthy women are examined for signs of breast cancer. As technology advances, signs of other cancers (such as prostate cancer, which generates antigens in the urine) can be checked long before symptoms appear. DNA will make diagnosis easier, with tests for a wide variety of diseases, either inherited or the result of mutations in body cells themselves. Once a patient or someone worried about a family problem turns up, DNA is just another weapon in the doctor's armoury. Medicine has already opened up, with home blood-pressure and cholesterol kits. Home pregnancy tests are in some senses already genetic screens, for many positive results end in termination, whatever the genes of the foetus. In the United States, over-the-counter tests are available for cystic fibrosis carrier status and for genes that predispose to breast cancer.

The technology to sell many more has arrived. Gene chips, is they are known, set out an array of probes for thousands of different genes at once. The idea began in the 1970s. A particular sequence of DNA is held in a stable in.mix, and possible matches, each one labelled with a r.ulio;icrivc probe or a fluorescent dye, floated past until one binds to it, in a sort of fishing for genes. Now, ten thousand bait sequences can be put on a single glass slide using methods developed by the computer industry. In principle one chip could test for all the common generic conditions at once; and, although no doubt they will be expensive, such devices may soon be on the market. The companies involved, some say, exaggerate risks and play on fears to increase sales. A test for a hereditary breast cancer gene costs $2500, far more than it costs to produce. Even so, their use will be hard to control, and in surveys most people think that they should be available. The interval between the discovery of a gene and the sale of a test is short and doctors will have to deal more and more with those who have, rightly or wrongly, diagnosed themselves or their children as at risk.

Medicine might gain from such information as it allows treatment to be targeted more accurately. To tailor pill to patient may become common. The ability to deal with anti-cancer drugs varies fifty-fold and a dose helpful to one individual may be fatal to another. For a certain drug used against leukaemia one child in ten has a low tolerance, so that the screen is essential. On the other hand, drugs not much used now because of their toxicity may turn out to be safe for some. The new approach might also change people's jobs. Nobody wants to be a passenger in an aeroplane with a colour-blind pilot and those with the gene do not get the job, for their own safety and that of others. That logic could extend a long way. People who inherit certain forms of the alpha-i antitrypsin enzyme find it hard to deal with dust or pollution. In the same way, some individuals with particular forms of the proteins used to make poisons safe are more susceptible to industrial carcinogens. Genetic screens might become part of employment and the tests become a company's duties. However, genes might also be used as an excuse not to improve the environment. The journal Chemical Week once wrote that '… it makes no economic sense to spend millions of dollars to tighten up a process which is dangerous only for a tiny fraction of employees… if the susceptible individuals can identified and isolated from it.'

In the United States and elsewhere, employers pay tor their employee's health insurance. Insurance, of any kind, is a mechanism for diffusing risk. The cost of an accident is diluted by sharing it with those who never make a claim. Those who enjoy driving drunk or keeping gold bars under the bed pay more and do not complain (much) that their lifestyle forces them to do so. But what about health insurance? In the USA (and more and more in Britain), access to medical care is limited by the ability to pay. Twenty million Americans must buy their own cover and tens of millions have no health insurance at all. Anyone buying a policy is asked to disclose any medical problems of which they are aware. Many applications are denied, and for the remainder all 'pre-existing conditions' — reported or not — are excluded.