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Purifying tRNA


Making mutant spectra with acid
Sydney Brenner Scientist
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However, this was very exciting because we would be talking… saying, 'Well, we've got this gene, which is the R2, and we've got this protein', and the protein was part of the phage, we had... but of course we had the wrong gene and the wrong protein, so now what we must do is either find the right protein and get the gene for this, which is actually what happened after many hiccups, or we must try and find the R2 protein. But in the meantime we were working… had started work on chemical mutagenesis. Now, Seymour had been doing work on the induction of mutants by chemicals before he came and had shown that if you incorporated 5-Bromouracil into the phage, you got mutants. If you treated it with various reagents you got mutants and so on, and what had been developed was this idea of mutational spectra and we had also started some work on this but not… in a desultory way. What was the idea? The idea was not only would we tell the co-linearity but we'd actually decode the protein this way you see so if we could get a chemical reagent that we knew changed guanine to adenine, you know that is made that mutation, and we could then see what amino acid changed, we will have then been able to work out the genetic code. That was the dream. Now I have to say it never got done that way or just excepting one thing which... which came later and not by… so the idea was let's do chemical mutagenesis. We had all of these spectra, and the question was: what did these spectra mean? One remarkable thing is that the induced mutants were at different places from the spontaneous mutants, and what we knew was that the induced mutants could be made to revert by the same class of reagents that induced them but none of the spontaneous mutants could be made to revert by the so-called base analogue mutagens, and this was a great puzzle. So I thought we must go and do something completely different, so I said to Seymour, 'You know there this is dye proflavine which I've been interested in for many time – it combines with DNA and there's a paper by Bob DeMars'. Proflavine also interferes with phage assembly; we knew that as well. Now since there was a paper by Bob DeMars… he says he's made mutants with proflavine, so why don't we do an R2 spectrum? And Lesley Barnett started then to do this, started to make mutants with proflavine and started to map them and what do you know we found that none of these proflavine mutants could be induced to revert by base analogues and none of the base analogue mutants could be induced to revert by proflavine. So we had these two spectra and this proflavine, and this was very hard to explain and at the time we were exploring then other reagents. We made mutant spectra with hydrazine, with acid… with photodynamic inactivation. I remember I made mutants with acid, but just by treating them at pH4.5. You… you get the phage, we know that this pH bases are removed, they get depurinated and then from these you can get mutants. I then measured the pH of Coca-Cola and I discovered it's considerably lower than 4.5, so I thought of writing up a paper on acid mutagenesis, saying I had done this by putting bacteriophages in Coca-Cola and here we are we have these Coca-Cola induced mutants and sending it to the Coca-Cola company saying, 'I'm at a loss to know where to publish this, have you any useful suggestions?' Needless to say, we didn't do it, but of course it would be interesting today, and I'm jolly sure that Coca-Cola will induce mutants as well; I mean vinegar on chips, that's the worst thing you can do. However, this is… that's aside. So we did many of these things and at the same time we were working on this.

South African Sydney Brenner (1927-2019) was awarded the Nobel Prize in Physiology or Medicine in 2002. His joint discovery of messenger RNA, and, in more recent years, his development of gene cloning, sequencing and manipulation techniques along with his work for the Human Genome Project have led to his standing as a pioneer in the field of genetics and molecular biology.

Listeners: Lewis Wolpert

Lewis Wolpert is Professor of Biology as Applied to Medicine in the Department of Anatomy and Developmental Biology of University College, London. His research interests are in the mechanisms involved in the development of the embryo. He was originally trained as a civil engineer in South Africa but changed to research in cell biology at King's College, London in 1955. He was made a Fellow of the Royal Society in 1980 and awarded the CBE in 1990. He was made a Fellow of the Royal Society of Literature in 1999. He has presented science on both radio and TV and for five years was Chairman of the Committee for the Public Understanding of Science.



Listen to Lewis Wolpert at Web of Stories



Tags: Coca-Cola, Seymour Benzer, Lesley Barnett, Bob Demars

Duration: 5 minutes, 8 seconds

Date story recorded: April-May 1994

Date story went live: 24 January 2008