Crick here discussed continued efforts to decipher the genetic code, in particular the use of base-equivalents such as bromouracil
(chemically very similar to the base uracil in RNA) to induce mutations, specifically the substitution of one base by another.
The second laboratory method mentioned was the synthesis of strands of RNA of known, simple, repetitive sequence (Crick here
referred to poly AU) as a means of finding out which triplets of bases code for which amino acids (a sequence of AUAUAUAUA
etc. codes for the polypeptide isoleucine-tyrosine-isoleucine-tyrosine etc).
Number of Image Pages:
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1962-02-09 (February 9, 1962)
Original Repository: Wellcome Library for the History and Understanding of Medicine. Francis Harry Compton Crick Papers
Many thanks for your very interesting paper on bromouracil substitution. I am delighted to see that you have refuted Chargaff's
nonsense. The results on the incorporation of G's in pairs is very puzzling. One gets the impression that G goes in
more easily at the beginning of the incubation than at the end. I wonder if a brief attack by the Lehman enzyme on the primer
would reduce this. I hope to have some better ideas before I get to California.
Would you thank Baldwin for his three papers. The reference to me is quite in order. I found them hard work to read because
they are so stuffed with results, but really very convincing.
Alex Shedlovsky has prepared the RNA polymerase to use with your poly AT, but we do not yet have the poly AU to test in the
Nirenberg system. We are now afraid it may not work because it may be two-stranded. I expect Paul Berg has already tried
this in any case.
I leave for the States on Monday. Looking forward to seeing you in April.