There are several things about that story that are disturbing. The first is the falsely happy ending. The woman does have the mutation.
She faces a death sentence, whether by her hand or much more slowly. She cannot escape her fate, however nicely she is treated by the experts. And surely the knowledge about her condition is hers to do with as she wishes. If she wishes to act on it and kill herself, who are the doctors to withhold the information? Yet they did the
'right thing', too. Nothing is more sensitive than the results of a test for a fatal disease; telling people the result starkly and coldly F A T E 6 3
may well not be the best thing to do - for them. Testing without counselling is a recipe for misery. But above all the tale drives home the uselessness of diagnosing without curing. The woman thought she was all right. Suppose she had five more years of happy ignorance ahead of her; there is no point in telling her that after that she faces lurching madness.
A person who has watched her mother die from Huntington's disease knows she has a fifty per cent chance of contracting it. But that is not right, is it? No individual can have fifty per cent of this disease. She either has a one hundred per cent chance or zero chance, and the probability of each is equal. So all that a genetic test does is unpackage the risk and tell her whether her ostensible fifty per cent is actually one hundred per cent or is actually zero.
Nancy Wexler fears that science is now in the position of Tiresias, the blind seer of Thebes. By accident Tiresias saw Athena bathing and she struck him blind. Afterwards she repented and, unable to restore his sight, gave him the power of soothsaying. But seeing the future was a terrible fate, since he could see it but not change it. 'It is but sorrow', said Tiresias to Oedipus, 'to be wise when wisdom profits not.' Or as Wexler puts it, 'Do you want to know when you are going to die, especially if you have no power to change the outcome?' Many of those at risk from Huntington's disease, who since 1986 can have themselves tested for the mutation, choose ignorance. Only about twenty per cent of them choose to take the test. Curiously, but perhaps understandably, men are three times as likely to choose ignorance as women. Men are more concerned with themselves rather than their progeny.12
Even if those at risk choose to know, the ethics are byzantine.
If one member of a family takes the test, he or she is in effect testing the whole family. Many parents take the test reluctantly but for the sake of their children. And misconceptions abound, even in textbooks and medical leaflets. Half your children may suffer, says one, addressing parents with the mutation. Not so: each child has a fifty per cent chance, which is very different. How the result of the test is presented is also immensely sensitive. Psychologists have 6 4 G E N O M E
found that people feel better about being told they have a three-quarter chance of an unaffected baby than if they are told they have a one-quarter chance of an affected one. Yet they are the same thing.
Huntington's disease is at the far end of a spectrum of genetics.
It is pure fatalism, undiluted by environmental variability. Good living, good medicine, healthy food, loving families or great riches can do nothing about. Your fate is in your genes. Like a pure Augustinian, you go to heaven by God's grace, not by good works.
It reminds us that the genome, great book that it is, may give us the bleakest kind of self-knowledge: the knowledge of our destiny, not the kind of knowledge that you can do something about, but the curse of Tiresias.
Yet Nancy Wexler's obsession with finding the gene was driven by her desire to mend it or cure it when she did find it. And she is undoubtedly closer to that goal now than ten years ago. 'I am an optimist', she writes,4 'Even though I feel this hiatus in which we will be able only to predict and not to prevent will be exceedingly difficult . . . I believe the knowledge will be worth the risks.'
What of Nancy Wexler herself? Several times in the late 1980s, she and her elder sister Alice sat down with their father Milton to discuss whether either of the women should take the test. The debates were tense, angry and inconclusive. Milton was against taking the test, stressing its uncertainties and the danger of a false diagnosis.
Nancy had been determined that she wanted the test, but her determination gradually evaporated in the face of a real possibility. Alice chronicled the discussions in a diary that later became a soul-searching book called
C H R O M O S O M E 5
E n v i r o n m e n t
Errors, like straws, upon the surface flow;
He who would search for pearls must dive below.
It is time for a cold shower. Reader, the author of this book has been misleading you. He has repeatedly used the word 'simple' and burbled on about the surprising simplicity at the heart of genetics.
A gene is just a sentence of prose written in a very simple language, he says, preening himself at the metaphor. Such a simple gene on chromosome 3 is the cause, when broken, of alkaptonuria. Another gene on chromosome 4 is the cause, when elongated, of Huntington's chorea. You either have mutations, in which case you get these genetic diseases, or you don't. No need for waffle, statistics or fudge.
It is a digital world, this genetics stuff, all particulate inheritance.
Your peas are either wrinkled or they are smooth.
You have been misled. The world is not like that. It is a world of greys, of nuances, of qualifiers, of 'it depends'. Mendelian genetics is no more relevant to understanding heredity in the real world than Euclidean geometry is to understanding the shape of an oak tree.
6 6 G E N O M E
Unless you are unlucky enough to have a rare and serious genetic condition, and most of us do not, the impact of genes upon our lives is a gradual, partial, blended sort of thing. You are not tall or dwarf, like Mendel's pea plants, you are somewhere in between. You are not wrinkled or smooth, but somewhere in between. This comes as no great surprise, because just as we know it is unhelpful to think of water as a lot of little billiard balls called atoms, so it is unhelpful to think of bodies as the products of single, discrete genes. We know in our folk wisdom that genes are messy. There is a hint of your father's looks in your face, but it blends with a hint of your mother's looks, too, and yet is not the same as your sister's - there is something unique about your own looks.
