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The Marshall W. Nirenberg Papers

Letter from Francis Crick to Marshall W. Nirenberg pdf (67,031 Bytes) transcript of pdf
Letter from Francis Crick to Marshall W. Nirenberg
In this letter, Crick shares the problems his team has encountered with evidence of degeneracy, and extends the hope of discussing the issue with Nirenberg in the future.
Number of Image Pages:
1 (67,031 Bytes)
1962-01-29 (January 29, 1962)
Crick, Francis
Nirenberg, Marshall W.
Reproduced with permission of Francis Crick.
Medical Subject Headings (MeSH):
Poly U
Exhibit Category:
Synthetic RNA and the Poly-U Experiments, 1959-1962
Metadata Record Letter from Francis Crick to Marshall W. Nirenberg (January 29, 1962) (in The Francis Crick Papers) pdf (94,320 Bytes) transcript of pdf
Box Number: 4
Folder Number: 31
Unique Identifier:
Accession Number:
Document Type:
Letters (correspondence)
Physical Condition:
Series: Series II: Correspondence, 1953-1993
Folder: General, 1953-1977
29th January, 1962.
Dear Dr. Nirenberg,
Thank you for your revised paper. We, too, thought we had evidence for degeneracy, as in our hands both poly (U,C) and Poly (U,A) incorporate leucine, and the result is not due to an impurity in the isotope. However, the argument obviously depends upon poly U not incorporating leucine, so we retested this. To our surprise and annoyance we found that our poly U does stimulate the incorporation of some leucine. The amount varies but on one occasion it was as high as 25% of the phenyalalamine incorporated.
Naturally we believe that the result with poly U is an artefact, but we have not been able to track it down. Until we have done this we don't feel we can trust the evidence from the other polymers.
As far as we can see the result is not due to impurities in our poly U. Apart from the fact that the polymers have been analyzed by Marianne we do not find the incorporation of other amino acids which we should expect if other bases were present in our poly U.
I hope by the time we meet we shall have found the cause of the trouble.
Looking forward to discussing all this with you.
Yours sincerely,
F. H. C. Crick
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