Fred Sanger on Developing Methods for Determining Nucleotide Sequences
  Fred Sanger     Biography    
Recorded: 16 Jun 2005

I think as particularly what we called the central dogma was becoming known. I worked on proteins and I worked on other proteins and chemistry of proteins. And at that time it was fairly clear that the other very important projects that involved sequencing and I was sort of interested in sequencing and I sort of got a love of sequencing, I think. So it seemed to me that the important thing was to try and sequence the nucleic acids and I started on—well, it was much more difficult you see, because there were only the four, in DNA, for instance, there are only the four components and all of them are very large molecules. So there was no obvious way to do it by the sort of methods that I had used for proteins. So we had to think about different, learn about the chemistry of the RNA and DNA. We started off on RNA because there were these small RNAs, the transfer RNAs, and one could get those and it was possible to purify them. There were about 50 residues long. The insulin actually had about fifty amino acids. So we started working on that. We weren’t terribly successful. Other people were working on them too. But we did manage to develop a few techniques. The sort of general approach we had was what we called the shotgun method; break up the molecule into small bits and looked at the small bits and then fit them together and then tried to deduce the whole sequence. That was the sort of approach we used for proteins. And that was the same type of general approach we used for these transfer RNAs and that worked to some extent, but it was fairly tedious and it involved a lot of fractionation. The main sort of technical problem is to separate these very complicated mixtures that you get.

Eventually, of course, the ultimate thing that we wanted to do was to sequence DNA because—I mean, by that time it was known how important DNA was. When we started, I think, we didn’t really know that DNA was the genetic material, but gradually it was clear and about in the 1960s and 1970s we were starting to think about DNA. But the smallest DNA, of course, is about 5,000—the smallest DNA that you get in a pure form is about 5,000 nucleotides long, much longer than anything we’d worked on before. The proteins, you see, we started off with some 50 and got—I mean, people were working on bigger proteins, but nothing as big as that. And there was the problem that, you know, there were only the four components in the DNA and all of these had to be distinguished. So we tried various methods which involved what we call partial hydrolysis, which is breaking up the molecule and separating them into fragments as best you can, and we got a certain amount of success. But never enough to really look into a genome or anything like that.

And I suppose it was about nearly 1970s, I developed this other technique which meant that you could actually read off the sequence from some—well, its a complicated story really. What we called the dideoxy method.

Frederick Sanger, OM, CH, CBE, FRS (born 13 August 1918) is an English biochemist and twice a Nobel laureate in chemistry. In 1958 he was awarded a Nobel prize in chemistry "for his work on the structure of proteins, especially that of insulin". In 1980, Walter Gilbert and Sanger shared half of the chemistry prize "for their contributions concerning the determination of base sequences in nucleic acids". The other half was awarded to Paul Berg "for his fundamental studies of the biochemistry of nucleic acids, with particular regard to recombinant-DNA".

He is the fourth (and only living) person to have been awarded two Nobel Prizes, either wholly or in part.