James Watson: How we discovered DNA

【微信公众号：Raz英语学习俱乐部（微信号Razkids）同步推送每日TED文稿和音频，关注Raz分级读物、TED学习系列、海外自由行/夏令营】 Nobel laureate James Watson took part in one of the most important scientific breakthroughs of the 20th century: the discovery of the structure of DNA. More than 50 years later, he continues to investigate biology&`&s deepest secrets. *Why you should listen James Watson has led a long, remarkable life, starting at age 12, when he was one of radio&`&s high-IQ Quiz Kids. By age 15, he had enrolled in the University of Chicago, and by 25, working with Francis Crick (and drawing, controversially, on the research of Maurice Wilkins and Rosalind Franklin), he had made the discovery that would eventually win the three men the Nobel Prize. Watson and Crick&`&s 1953 discovery of DNA&`&s double-helix structure paved the way for the astounding breakthroughs in genetics and medicine that marked the second half of the 20th century. And Watson&`&s classic 1968 memoir of the discovery, The Double Helix, changed the way the public perceives scientists, thanks to its candid account of the personality conflicts on the project. From 1988 to 1994, he ran the Human Genome Project. His current passion is the quest to identify genetic bases for major illnesses; in 2007 he put his fully sequenced genome online, the second person to do so, in an effort to encourage personalized medicine and early detection and prevention of diseases. *Transcript Well, I thought there would be a podium, so I&`&m a bit scared. (Laughter) Chris asked me to tell again how we found the structure of DNA. And since, you know, I follow his orders, I&`&ll do it. But it slightly bores me. (Laughter) And, you know, I wrote a book. So I&`&ll say something -- (Laughter) -- I&`&ll say a little about, you know, how the discovery was made, and why Francis and I found it. And then, I hope maybe I have at least five minutes to say what makes me tick now. In back of me is a picture of me when I was 17. I was at the University of Chicago, in my third year, and I was in my third year because the University of Chicago let you in after two years of high school. So you -- it was fun to get away from high school -- (Laughter) -- because I was very small, and I was no good in sports, or anything like that. But I should say that my background -- my father was, you know, raised to be an Episcopalian and Republican, but after one year of college, he became an atheist and a Democrat. (Laughter) And my mother was Irish Catholic, and -- but she didn&`&t take religion too seriously. And by the age of 11, I was no longer going to Sunday Mass, and going on birdwatching walks with my father. So early on, I heard of Charles Darwin. I guess, you know, he was the big hero. And, you know, you understand life as it now exists through evolution. And at the University of Chicago I was a zoology major, and thought I would end up, you know, if I was bright enough, maybe getting a Ph.D. from Cornell in ornithology. Then, in the Chicago paper, there was a review of a book called "What is Life?" by the great physicist, Schrodinger. And that, of course, had been a question I wanted to know. You know, Darwin explained life after it got started, but what was the essence of life? And Schrodinger said the essence was information present in our chromosomes, and it had to be present on a molecule. I&`&d never really thought of molecules before. You know chromosomes, but this was a molecule, and somehow all the information was probably present in some digital form. And there was the big question of, how did you copy the information? So that was the book. And so, from that moment on, I wanted to be a geneticist -- understand the gene and, through that, understand life. So I had, you know, a hero at a distance. It wasn&`&t a baseball player; it was Linus Pauling. And so I applied to Caltech and they turned me down. (Laughter) So I went to Indiana, which was actually as good as Caltech in genetics, and besides, they had a really good basketball team. (Laughter) So I had a really quite happy life at Indiana. And it was at Indiana I got the impression that, you know, the gene was likely to be DNA. And so when I got my Ph.D., I should go and search for DNA. So I first went to Copenhagen because I thought, well, maybe I could become a biochemist, but I discovered biochemistry was very boring. It wasn&`&t going anywhere toward, you know, saying what the gene was; it was just nuclear science. And oh, that&`&s the book, little book. You can read it in about two hours. And -- but then I went to a meeting in Italy. And there was an unexpected speaker who wasn&`&t on the program, and he talked about DNA. And this was Maurice Wilkins. He was trained as a physicist, and after the war he wanted to do biophysics, and he picked DNA because DNA had been determined at the Rockefeller Institute to possibly be the genetic molecules on the chromosomes. Most people believed it was proteins. But Wilkins, you know, thought DNA was the best bet, and he showed this x-ray photograph. Sort of crystalline. So DNA had a structure, even though it owed it to probably different molecules carrying different sets of instructions. So there was something universal about the DNA molecule. So I wanted to work with him, but he didn&`&t want a former birdwatcher, and I ended up in Cambridge, England. So I went to Cambridge, because it was really the best place in the world then for x-ray crystallography. And x-ray crystallography is now a subject in, you know, chemistry departments. I mean, in those days it was the domain of the physicists. So the best place for x-ray crystallography was at the Cavendish Laboratory at Cambridge. And there I met Francis Crick. I went there without knowing him. He was 35. I was 23. And within a day, we had decided that maybe we could take a shortcut to finding the structure of DNA. Not solve it like, you know, in rigorous fashion, but build a model, an electro-model, using some coordinates of, you know, length, all that sort of stuff from x-ray photographs. But just ask what the molecule -- how should it fold up? And the reason for doing so, at the center of this photograph, is Linus Pauling. About six months before, he proposed the alpha helical structure for proteins. And in doing so, he banished the man out on the right, Sir Lawrence Bragg, who was the Cavendish professor. This is a photograph several years later, when Bragg had cause to smile. He certainly wasn&`&t smiling when I got there, because he was somewhat humiliated by Pauling getting the alpha helix, and the Cambridge people failing because they weren&`&t chemists. And certainly, neither Crick or I were chemists, so we tried to build a model. And he knew, Francis knew Wilkins. So Wilkins said he thought it was the helix. X-ray diagram, he thought was comparable with the helix. So we built a three-stranded model. The people from London came up. Wilkins and this collaborator, or possible collaborator, Rosalind Franklin, came up and sort of laughed at our model. They said it was lousy, and it was. So we were told to build no more models; we were incompetent. (Laughter) And so we didn&`&t build any models, and Francis sort of continued to work on proteins. And basically, I did nothing. And -- except read. You know, basically, reading is a good thing; you get facts. And we kept telling the people in London that Linus Pauling&`&s going to move on to DNA. If DNA is that important, Linus will know it. He&`&ll build a model, and then we&`&re going to be scooped. And, in fact, he&`&d written the people in London: Could he see their x-ray photograph? And they had the wisdom to say "no." So he didn&`&t have it. But there was ones in the literature. Actually, Linus didn&`&t look at them that carefully. But about, oh, 15 months after I got to Cambridge, a rumor began to appear from Linus Pauling&`&s son, who was in Cambridge, that his father was now working on DNA. And so, one day Peter came in and he said he was Peter Pauling, and he gave me a copy of his father&`&s manuscripts. And boy, I was scared because I thought, you know, we may be scooped. I have nothing to do, no qualifications for anything. (Laughter) And so there was the paper, and he proposed a three-stranded structure. And I read it, and it was just -- it was crap. (Laughter) So this was, you know, unexpected from the world&`&s -- (Laughter) -- and so, it was held together by hydrogen bonds between phosphate groups. Well, if the peak pH that cells have is around seven, those hydrogen bonds couldn&`&t exist. We rushed over to the chemistry department and said, "Could Pauling be right?" And Alex Hust said, "No." So we were happy. (Laughter) And, you know, we were still in the game, but we were frightened that somebody at Caltech would tell Linus that he was wrong. And so Bragg said, "Build models." And a month after we got the Pauling manuscript -- I should say I took the manuscript to London, and showed the people. Well, I said, Linus was wrong and that we&`&re still in the game and that they should immediately start building models. But Wilkins said "no." Rosalind Franklin was leaving in about two months, and after she left he would start building models. And so I came back with that news to Cambridge, and Bragg said, "Build models." Well, of course, I wanted to build models. And there&`&s a picture of Rosalind. She really, you know, in one sense she was a chemist, but really she would have been trained -- she didn&`&t know any organic chemistry or quantum chemistry. She was a crystallographer. And I think part of the reason she didn&`&t want to build models was, she wasn&`&t a chemist, whereas Pauling was a chemist. And so Crick and I, you know, started building models, and I&`&d learned a little chemistry, but not enough. Well, we got the answer on the 28th February &`&53. And it was because of a rule, which, to me, is a very good rule: Never be the brightest person in a room, and we weren&`&t. We weren&`&t the best chemists in the room. I went in and showed them a pairing I&`&d done, and Jerry Donohue -- he was a chemist -- he said, it&`&s wrong. You&`&ve got -- the hydrogen atoms are in the wrong place. I just put them down like they were in the books. He said they were wrong. More transcript please see: http://www.ted.com/talks/james_watson_on_how_he_discovered_dna/transcript?language=en