For example, cystic fibrosis has been linked to more than 1,000 different mutations. It is also the case that many people who harbour the potential for genetic disease choose not to be tested. In the case of Huntingdon's chorea it is only a very small minority. This may seem strange but then this is another of those facts of human nature that not even the DNA map can explain. But behind these predictions of wiping away all our tears, lies an implied belief in human perfectibility, the corralling of at least one of the four horsemen of the apocalypse - disease in its widest sense of not the physical but other kinds of human defect.
Genetic engineering raises the question of the place of suffering in our world.
We are being assured, of course, that eugenics is now so discredited by its Nazi past and the horrors perpetrated in Sweden and the US in the 1920s and 1930s that no state will now countenance it. Perhaps not as an instrument of public policy. But cosmetic operations have been performed, at parents' request, on children with Down's syndrome to remove Down's features. Women with learning difficulties have been sterilised without their consent. Suffering is all around us, much of it not preventable by scientific or other means - loss, misfortune, death, increasing incapacity.