In this letter Yanofsky reported results of experiments with DNA that, after undergoing either a spontaneous mutation in its
order of nucleotides or a mutation induced by ultraviolet light, no longer coded for the amino acid that it originally specified
in the polypeptide, but rather for a different amino acid.
Number of Image Pages:
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1965-05-10 (May 10, 1965)
Original Repository: Wellcome Library for the History and Understanding of Medicine. Francis Harry Compton Crick Papers
The same Gly --UV--> Glu --spont--> Ala, Val, Gly (only Glu --> Gly with 2 AP + 5 BDU)
The same Gly --UV--> Val (only once)
The Val from Glu --spont--> Gly, Ala
The above Ala --UV--> Glu
The above Ser --UV--> Arg
Gly --UV--> Val
Val --spont--> Gly, Ala
Gly --UV--> Asp, Cys
Asp --spont--> Gly, Ala (only Asp --> Gly increased by 2 AP)
Cys --spont--> Gly (not increased by 2 AP)
Thr --EMS--> Ileu
Ileu --> Thr, Ser, Asp (only Ileu --> Thr by 2 AP)
This is the Asp you doubted. The evidence that it is Asp is as follows: At pH 6.8 the Asp peptide is clearly negatively
charged relative to the wt peptide.
However, in view of the disagreement with the coding data we are in the process of looking at papain fragments to be doubly
sure. There is the slim possibility which we certainly haven't excluded, that there are two changes in the peptide (Ala-Gly-Val-Thr-Gly-Ala-Glu-Asn-Arg)
Ileu --> Asn and Asn --> Asp.
Tyr --spont--> Cys
Cys --spont--> Tyr (Increased by 2AP)
Leu --spont--> Arg
Ser --UV--> Leu
We have one paper in press that is pertinent, but the observations are summarized above as Set 3.
I just heard about Streisinger's result which should be conclusive -- I wasn't convinced by Schweet or Rich -- their
data was suggestive at best. We are repeating the crosses with better outside markers. I'll let you know as soon as
we have any results.*
If AGA is the Arg of Set 1, the only disagreements between our observation and the code you sent and the almost identical
one Nirenberg has in press are (1) infrequent mutation of Arg --> Thr ACA (Incidentally AUA almost certainly is Ileu from
(2) Arg x Val cross --> Gly + Ser. The best explanation is that Val (GGA) mutated to Val (GGPyrimidine). The Val stock
used in the cross was used as a standard lab reference stock for at least a year and I guess it could have changed, although
it would seem unlikely.
(3) The presumed Ilue --> Asp change discussed above. There's one other cross we haven't published.
Thr x Glu (both Set 1) --> 4 recomb. analyzed, 3 Ala, 1 Gly (a revertant?)
That's it! I'll keep you posted on anything else of relevance that turns up.