Interviewee: James Watson. James Watson talks about how he worked out the base pairing of DNA. (DNAi Location: Code > Finding the structure > players > James Watson and Francis Crick > Base pairing)

Well, it's too much effort to draw them out on paper each time and get the bond angles and bond lengths right, best to, you know, make out some cardboard cut outs. So I just used ordinary sort of thin pieces of white covered smooth cardboard, and attached to them hydrogen atoms, I made these six to nine member rings and then distinguished adenine and guanine or thymine and... by little sticks which said here is a hydrogen atom at the tip and if you have a good hydrogen bond it should immediately, it should point directly at the acceptor. And so I finally put those together, didn't really have them in good shape until early Saturday morning February 28th. I got in early and finally was going to see which one fits together. And Francis had kept telling me, well you know, there's Chargaff's pairs, would they pair to each other. And, but I didn't like Chargaff, ever since I had met him a year before, I thought I don't want to use his data in finding the structure, boy it was really stupid. And, but I couldn't help, you know, just switching around on the table to see that adenine and thymine had a, formed a very nice base pair and guanine and cytosine formed one identical in shape, and I thought you can build a double helix with adenine and thymine and guanine and cytosine base pairs.

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