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The Francis Crick Papers

Letter from James D. Watson to Francis Crick pdf (1,146,467 Bytes) transcript of pdf
Letter from James D. Watson to Francis Crick
Item is handwritten. Item is a photocopy.
Number of Image Pages:
5 (1,146,467 Bytes)
1954-02-13 (February 13, 1954)
Watson, James D.
Crick, Francis
Original Repository: Wellcome Library for the History and Understanding of Medicine. Francis Harry Compton Crick Papers
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Reproduced with permission of James D. Watson.
Exhibit Category:
Defining the Genetic Coding Problem, 1954-1957
Box Number: 72
Folder Number: PP/CRI/H/1/42/3
Unique Identifier:
Document Type:
Letters (correspondence)
Physical Condition:
Series: Notes and Drafts
SubSeries: Notes and Drafts 1950-1955
SubSubSeries: [Miscellaneous Papers Photocopied by Aaron Klug]
Folder: [Letters to Crick from James Watson]
February 13, 1954
Dear Francis,
I now understand 1/2 of RNA. Consider the following (1) in RNA from plant viruses the base ratios are not complementary (2) in RNA from all other sources the ratios are complementary. This is not an obvious fact as much of the data is sloppy but the good papers show the ratios and are the ones to be considered. The conclusive data are in Smellie (it smells right!!) and Davidson Biochem J. (May 1953). 3) The x-ray diagrams (both powder and fibre [sic]) from both complementary and non complementary RNA are identical
From this we can deduce
[writing cut off on bottom line, possibly (over)]
1) the structure of the non complementary RNA cannot be two stranded and complementary. In fact it is likely a one stranded helix (the x-ray pattern is horribly helical
2) the complementary must also exist (at least after isolation) in the single stranded form.
3) both types will however replicate by complements. The 2 stranded form we shall postulate to be less permanent than the one stranded beast.
4) the plant viruses contain only one of the two possible complements and always the same one. This seems phony but I see no way out.
We must find out
1) the structure of the one stranded form. We have a structure which is neither very ugly nor very cute but which seems to vaguely agree with
Delbruck. The others are not convinced but are not intuative [sic] creatures, and so do not count. I do not believe the base ratios could be so good if they did not imply self replication -- Also cannot believe in 2 ways for RNA to replicate. hence do not mind the asymmetry in Plant Virus picture. Also it would be strange for DNA and RNA to be so similar and yet have different replication schemes.
I think this idea is worth letter to Nature which I am now writing. Do you agree? This again shows value of reading over expts. Idea came 3 days ago after spending 3 days reading all literature on base analysis: Chargaff [?] has failed again!!! Really very funny. The important thing is to ignore data which complicates life.
2) the structure of the two stranded beast. This may be nasty since we have no x-rays but is worth the effort since this may be the beast which grows proteins. In any case we now visualize the mysteries of life as follows
this is why we find 2 strands one to keep code. the other to be transformed to RNA which sneaks to cytoplasm and makes protein.
All of this is slightly mad but as it is cute I think it is correct: Your comments seriously desired. Have convinced Feynmann [sic] and slightly
what do we do after protein specificity is solved. I really do not want to do genetics or watch birds or think about phospho lipids
About you [sic] trip to Midwest. I did write Luria. He replied favorably and so I don't feel I can write again. I think it best for you to write directly.
It is now raining like hell. When not much smog. However life is not so depressing as initially. Even so L.A. is basically deadly. Am going to drunken brawl this evening and so it is good that I have written now and not planning to do so tomorrow.
Would feel best if you did not pass on contents of this letter until note to Nature is in
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