Date: 15 October 1980. Place: New York Stock Exchange. The launch of a small company called Genentech sparked frenetic business, driving up its share price from $35 to $89 within the first 20 minutes of trading. At the end of the day, each Genentech share was worth $71.25. Why was there so much interest in a small four-year-old Californian company specialising in genetic engineering?

Two years previously, scientists at Genentech had isolated the genes that code for the A and B polypeptide chains of human insulin, spliced them into a loop of bacterial DNA called a plasmid and inserted the modified plasmid into the bacterium Escherichia coli. They had achieved what previously had seemed impossible, but by today's standards is commonplace. An organism (E. coli) had been genetically engineered to produce a medicine (the hormone insulin used to treat diabetes) with a worldwide market worth many hundreds of millions of dollars a year. Before then, insulin could only be obtained from slaughtered cattle and pigs. It was expensive to produce and in limited supply. Also, the chemical structure of animal insulin is different from human insulin; some diabetics react allergically to it. Genentech's achievement seemed to open the way to the large-scale production of medicines which were reliable, cheap and, in the case of insulin, more suitable for the human patient. No wonder the New York Stock Exchange was frantic on that October day – the future promised not only medical progress but also unrivalled profits!