Modern Mind

say, or an insect), if inserted into the bacterium with ‘split rings,’ would be taken up. The significance of Cohen’s idea lay in the fact that the plasmid replicated itself many times in each cell, and the bacterium divided
every twenty minutes.
With this form of replication and division, more than a million copies of the spliced DNA could be created
within a day. 30
    After the lecture, Cohen sought out Boyer. As Walter Bodmer and Robin McKie tell the story, in their history of the genome project, the two microbiologists adjourned to a delicatessen near Waikiki Beach and, over corned beef sandwiches, agreed on a collaboration that bore its first fruits in the
Proceedings of the National Academy of Sciences
in November 1973, when they announced the first report of successful cloning. From now on there was enough DNA to experiment with. 31
    The next step – important both practically and theoretically – was to explore the
sequence
of bases in the DNA molecule. Sequencing was necessary because if biologists were to discover which genes governed which aspects of functioning, the exact order needed to be understood. Fred Sanger in Cambridge, England, and Walter Gilbert in Cambridge, Massachusetts (Harvard), both discovered methods of doing this, and both received a Nobel Prize for their efforts. But Sanger’s method was identified first and is the more widely used. * Earlier, Sanger had developed a way of identifying the amino acids that make up proteins, and this had earned him his first Nobel, when he discovered the structure of insulin. But that method was far too slow to work with DNA, which is a very long molecule. Moreover, it is made up from only four subunits (A, C, G, and T), so long sequences would need to be understood before they could be related to properties. His breakthrough was the creative use of chemicals called dideoxy, otherwise known as chain terminators.’ 32 These are in fact imperfect forms of adenine, cytosine, guanine, and thymine; when mixed with DNA polymerase, the DNA-copying enzyme, they form sequences, but incompletely – in fact they stop, are terminated, at either A, C, G, or T. 33 As a result they form DNA of varying lengths, each time stopping at the same base. Imagine, for the sake of argument, a strip of DNA that reads: CGTAGCATCGCTGAG. This, treated with adenine (A) terminators wouldproduce strips in which growth stops at positions 4, 7, and 15, whereas the thymine (T) terminator would produce strips where growth stops at 3, 8, and 12, and so on. The technique actually to separate out these different strands consisted of placing the DNA in a tray of special gel, in which an electrical field had been applied to opposite ends. DNA, being negatively charged, is attracted to the positive pole, with the smaller fragments pulled faster than the larger ones, meaning that the strands eventually separate out, according to size. The DNA is then stained, and the sequence can be read. The technique was announced in
Nature
on 24 February 1977, and it was from that moment, coming on top of the cloning experiments, that genetic engineering may be said to have begun. 34
    Just over a year later, on 24 August 1978, Genentech, founded by Boyer and a young venture capitalist called Robert Swanson, announced that it had produced human insulin by this method – gene sequencing and cloning – and that it had concluded a deal with Eli Lilly, the pharmaceutical giant, for the mass manufacture of the substance. Two years later, in October 1980, when Genentech offered 1,100,000 of its shares for sale to the public, another phase in the microbiological revolution was born: offered at $35 a share, the stock immediately jumped to $89, and Boyer, who had invested just $500 in the company in early 1974, saw the value of his 925,000 shares leap to more than $80 million. No physicist was ever worth so much. 35
    Compared with the electron and other fundamental particles, the gene had taken some time to be isolated and broken down into its component parts. But as with physics, the experimental and theoretical work went in tandem.
    Beginning in the 1970s a new form of literature began to appear. It grew out of Robert Ardrey’s works but was more ambitious. These were books of biology but with a distinct philosophical edge. However, they were not written by journalists, or dramatists, as Ardrey was, or Gordon Rattray Taylor was, in
The Biological Time Bomb,
or by scientific popularisers, as Desmond Morris