Frederick Sanger: I was only 40 when I won the Nobel Prize, and a lot of people, when they win a Nobel Prize, they get a big job as the head of a lab and usually give up doing research, but I didn’t want to do that, and I wouldn’t have been any good at it. So, I carried on doing research, and that was the sort of life I wanted to live, and I wasn’t going to retire at 40, and about that time — that was 1958 — about that time or shortly after — I’d been working on other proteins and doing things which didn’t amount to very much, but people got interested in nucleic acids, and these are really important components of living matter, and like proteins, they are built up of long chains, long chains off into sort of smaller fragments, smaller residues.

But in the case of DNA, what I finally ended up with, this has the four components which they call A, G, C, and T. These are chemical entities, and the sequence of these is what defines the language of the DNA. DNA is enormous in the case of any substance, compared with the protein side. So, it was a much more difficult problem. You had the four components, and you had to try and determine the order of them in DNA chains. I’d done a good deal of preliminary work on the other nucleic acid, which was RNA, which was smaller, and you could sort of use methods similar to the ones I’d used for the proteins, but it was fairly slow, and it wasn’t too easy. You see, if you’ve got only four components, four letters, as it were, in the language, then to get a meaningful sequence on something that is fairly big, you’ve got to get a fairly long piece out, and long pieces are difficult to fractionate, and we had very limited success using the type of method which we had used for proteins. So, eventually, we did get on to an entirely different method.