May 20, 1968

Professor and Mrs. Albert Tyler

Division of Biology

California Institute of Technology

Pasadena, California 91109

Dear Albert and Betty:

On page 13 you refer to early presentations of template concepts in synthesis, and refer to a couple of my papers and to the 1940 paper by Delbrück and me. I would be interested to know what you have found during your search of the literature as to the early published suggestion that the gene may consist of complementary molecules, each of which would act as a template for the synthesis of a duplicate of the other, in the process of gene duplication. A few years ago I saw a paper in the Proceedings of the Royal Society in which the author said that Watson and Crick had developed a completely new idea, in their paper on the double helix, the idea that the gene could consist of two complementary molecules, each of which could act as a template for the synthesis of a duplicate of the other. I wrote to him, sending him some of my papers in which this idea is mentioned, the first of which is, I think, the 1940 paper by Delbrück and me. He did not answer my letter. I am not sure, in fact, that our 1940 paper was the first one to make this suggestion. What have you discovered, in your search of the literature?

There is a statement on page 15 that is wrong. You say that Watson and Crick assumed pairing of purines and pyrimidines with hydrogen bonds joining A to T and G to C in the manner illustrated in your Fig. 4. In fact, they assumed hydrogen bonds joining G and C in a different way, with only two hydrogen bonds. Even some years later (Scientific American article) the incorrect structure with only two hydrogen bonds was being used by at least one of them. It was Corey and I who pointed out that the known structures of purines and pyrmidines require that there be three hydrogen bonds between G and C, as illustrated in your Fig. 4, and everybody has accepted this structure. I tried to get Crick to explain to me why they refused to accept three hydrogen bonds for the GC pair. He made a statement—something about acid-base properties of DNA, as shown by titration curve but it seemed to me not to be of much weight. In my Centennial Lecture at UCLA a few days ago I mentioned this episode, as showing that it is possible to make an important discovery even if some of your ideas are wrong.

I am sending you a copy of the volume Structural Chemistry and Molecular Biology, under separate cover.

Sincerely,

Linus

LP:jj

P.S. The paper by Delbrück and me is No. 31, listed on page 901 of the Festschrift. The paper about three hydrogen bonds between guanine and cytosine is No. 285, listed on page 902.