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![50 GEN Kit AL NATUllK OK THE GENETIC CODE INTRODUCTION AND DISCUSSION Dr. Stanley: Ladies and gentlemen, we are ready to begin our afternoon session with another real treat in store. Francis Crick, so far as I know, is not particularly trigger-happy, but that word came to my mind when 1 was thinking about a terminology that would describe his mind. I must say, I have never met anybody who was so quick mentally as I've known Francis Crick to be over the years. I imagine this is what paid oli a few years ago when Jim Watson came to Cambridge for a little stay, and it was the interplay of these two minds that resulted in a conception which I regard as being one of the truly great ones of modern times, and that's the Watson-Crick structure, the double helical structure, for DNA. It certainly has had a tremendous impact upon the minds of mankind, and scientists, of course, particularly. There is an extraordinary amount of work which has stemmed from this concept. Dr. Crick came into this work as a physicist. Dr. Watson, who, unfor tunately, is not here, came in as a biologist, a microbiologist. He received his degree with Dr. Luria- So I think the two were ideally equipped to deal with the problem of the structure of DNA at that time. Dr. Crick has ceased to become a straight x-ray man. When I was in his laboratory in 1961 for a few weeks, he was very busy pouring bacterial plates hour after hour, sometimes until the wee hours of the morning. He was studying acridine mutants in an attempt to establish the mode of reading of the DNA. Nobody watching him in those days would have thought that he had started out as a physicist* because he was an out and out biologist at that' time. Well, I need not¡ tell' you anything more about Dr. Crick. You have his biography here in the Booklet: li shalli now. call oni Dr. Crick to give his discussion of the General Nature ofl the Genetic Code : [iThe following discussion took place after Dr. Crick presented his address.] Dr. Stanley: Thank you very much, Div Crick, for this quite fascinating exposé on the General' Nature of the Genetic Codle. I should like to make a comment or two about the work that has gone on in the Virus Laboratory with tobacco mosaic virus. The active portion is, of course, an RNA, and it can be regarded as a messenger RNA. Tobacco mosaic virus, a nucleo- protein, has been available for years in pure form and from this a quite pure active RNA can be obtained. This viral RNA carries the message or information for making the protein overcoat! component of the virus. One of our objectives, which was started 1 some years ago, was to obtain F. H. C. CRICK the amino acid sequence of the protein of tobacco mosaic virus. This work was stimulated by Sanger's work on insulin. And as a result, about 1960, I think it was, we obtained the complete amino acid sequence of the 158 amino acids of the protein component of tobacco mosaic virus. Then Schuster in Tubingen, Germany reported that you could convert cytosine to uracil in RNA through deamination. A great many nitrous acid mutants of tobacco mosaic virus RNA were made in our laboratory, as well as in the Tubingen Laboratory. This gave an opportunity, in a preliminary way, to make some of the verifications that Dr. Crick has mentioned relating triplets to amino acids. We have, between the two laboratories, I think around 50 or 60 mutants, where the exact amino acid can be pinpointed in the 158 amino acids, that has been changed, presumably by virtue of a C to U conversion. The difficulty with tobacco mosaic virus is that you cannot conduct genetic experiments; you cannot do the necessary crossing experiments. This was the reason I am particularly pleased with the recent wcirk of Yanofsky of Stanford, for he combined chemistry and genetics in the very beautiful way that Dr- Cpiçk has indicated. I had hoped that Dr. Yanofsky ^vçuld be , here, but as has already been indicated, he stays in the laboratory at work i and doesn't tend to come to meetings. Biochemists are not nearly as backward as our friend, the physicist- turned-molecular-biologist, would indicate. I happen to know a graduate student who, two or three years ago, had separated and purified 15 or 20 of these triplets obtained from the hydrolysis of yeast nucleic acid. Unfortunately, things don't move quite as rapidly as sometimes the minds of some people move, but I am sure that all 64 triplets will be available eventually, and means will be found to test their activity in amino acid incorporating systems. We already, for example, know much about the terminal nucleotides in the tobacco mosaic virus nucleic acid and that may provide useful information. Now, in view of the vast amount of work that Dr. lOchoa has done ,o,n the genetic code, I wonder if he would care to make a ifew .comments, or ask a question. Dr. Severo Ochoa (Speaker), New York University School of Medicine: It was, as usual, a fascinating presentation by Francis tCriak, which we all have enjoyed xvery much. Now, as ¡Dr. Stanley .mentioned, a number of trinucleotides are available. They .have been isolated (from ,ribcmuclease. digests of RNA by Wendell M. Stariley, Jr., who is a .post-doQtoral student ,jn our laboratory.](https://iiif.wellcomecollection.org/image/b18178522_PP_CRI_M_1_3_0006.jp2/full/800%2C/0/default.jpg)
