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The Francis Crick Papers

Letter from Francis Crick to Severo Ochoa pdf (97,928 Bytes) transcript of pdf
Letter from Francis Crick to Severo Ochoa
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1 (97,928 Bytes)
1962-12-05 (December 5, 1962)
Crick, Francis
Ochoa, Severo
Original Repository: Wellcome Library for the History and Understanding of Medicine. Francis Harry Compton Crick Papers
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Reproduced with permission of the Wellcome Library for the History and Understanding of Medicine.
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Exhibit Category:
Deciphering the Genetic Code, 1958-1966
Metadata Record Letter from Severo Ochoa to Francis Crick (November 15, 1962) pdf (116,278 Bytes) transcript of pdf
Box Number: 10
Folder Number: PP/CRI/D/1/1/15
Unique Identifier:
Document Type:
Letters (correspondence)
Physical Condition:
Series: Correspondence
SubSeries: Alphabetical Correspondence
SubSubSeries: Correspondence 1
Folder: Correspondence O
5th December, 1962.
Dear Severo,
Thank you so much for the letter and the preprint. I must really congratulate you on the poly A-polylysine result. We are all kicking ourselves for having missed it. Naturally I am delighted that you are finding more triplets. You will remember that when I visited you last February I felt sure that there would be many more than the ones you had then. I am still not very happy about the identification of triplets, and feel that it is important to make polynucleotides with a range of compositions and not just 5:1 or 1:5.
As to the question of degeneracy I feel that if all the codons are triplets, and if, say AUC, ACC, AGC and AAC all stand for histidine (we would write this as A-C) nevertheless one would call this degeneracy. You will see that I discuss such possibilities in my review, including your point about transfer RNA (see pages 62 and 63). On the other hand if Robert's code were correct, i.e. a mixture of doublets and triplets, one for each amino acid, so that the reading sometimes moved on two steps and sometimes three, then I would agree that it should be called non-degenerate. However, I feel our genetic results make such a code unlikely. I wish I could penetrate the logic (if any) of the degeneracy but so far it has baffled me.
Off to Stockholm in a day or so. It will be quite a family affair this time.
With all good wishes,
F. H. C. Crick
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