From the 1984 lecture programme:
Many diseases have an inherited component. Some, such as Huntingdon's chorea, or muscular dystrophy, follow simple patterns of inheritance in families, which can now be traced using markers provided by genetic engineering techniques. This offers the possibility of detection very early in pregnancy and so abortion if the foetus is affected.
These approaches to treating genetic disease give rise to difficult moral decisions.
Most of the genetic differences between people are normal, and not connected with disease.They can, for example, be used to trace relationships between different populations.
In much the same way, differences between species measured at the genetic level tell us about their evolutionary relationships. The normal inherited differences must also contribute to all aspects of human variation, including behaviour, facial features, intelligence, musical ability, athletic prowess – the list is endless.
So far these variations have proved too complicated to be sorted out properly at the genetic level. But the new genetics will eventually identify all the human genes and their functions. How far will this take us in explaining the infinite variety of mankind?