From the 1984 lecture programme:
How can we isolate and study the genes one at a time? The answer is to "clone" them. Plant cuttings and bacterial colonies are clones, namely a population of cells all derived from the same initial cell by cell division.
Genetic engineers have found ways of cutting up DNA into identifiable pieces and inserting these one at a time into a bacterium. The inserted piece of DNA, a gene, then divides with the bacterium — it's been cloned.
Now, a human gene cloned in this way can be produced in pure form in unlimited amounts, since it is easily distinguished from the bacterial DNA. And the bacteria can be made to produce the human gene's product — insulin for treating diabetics, interferon for treating viral diseases or a growth hormone to make you grow bigger.
Genetic engineers can now clone and "read" any gene and it is only a matter of time before the whole human DNA language is read. That is a tremendous boost, not only for the biotechnology industry, but also for understanding the nature of all those differences between people.