In 1967, two years after the date of this letter, Crick, Sydney Brenner, and Alan Garen determined that the amber and ochre
codons mentioned in the last paragraph (the triplets UAG and UAA, respectively) signal the termination of the polypeptide
chain. They were called nonsense codons because it became clear from experiments with certain phage mutants that they do
not specify any amino acid during protein synthesis. The names amber and ochre were assigned to them randomly by researchers.
NOTE: The date was mistakenly typed as "7th January 1964." The actual date of this letter is 7 January 1965.
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7 January 1965
Original Repository: Wellcome Library for the History and Understanding of Medicine. Francis Harry Compton Crick Papers
Thank you for your letter of 4th January. I have noted what you say about the William T. Sedgwick Memorial Lecture. The
title is perfectly satisfactory. I also note that there is a dinner attached to it.
About social arrangements, I wrote to Jim yesterday about another matter and as I had not heard from you I suggested that
he should coordinate the various invitations. I am willing to fall in with any reasonable arrangements you make between you.
On your specific questions, I think it would be easier for everyone if I stayed at an hotel (I asked Jim to find me one).
I would certainly like to come to Walter Rosenblith's party on the Saturday evening.
It would be nice to have the direction of messenger reading cleared up. Sydney and the others are working hard trying to
discover the codon for the amber and ochre mutants. We have a good idea what they are and perhaps by the time I reach M.I.T.
we shall know rather more definitely.