January 15, 1962

Dr. Francis El. C. Crick
Univerrity of Cambridge
Department of Phyrrice
Cavendieh Laboratory
Pree School Lane
Cambridge, England

Dear Dr. Crick:

   David Davies has made all of the arrangements for your talk
here in February and we are all looking forward to seeing you.
Your paper on the General Nature of the Cenetic Code is beautiful.
Your findings with this system certainly agree well with our
results.  We have recently found that the code is partially
degenerate, at least with reepect to leucine, for both poly UC
and poly UC stimulate the incorporation of leucine into protein.
Also, we were able to show that nonsense exists for a number of
polynucleotides, including poly A, do not code for any amino
acid.  We revised our mnuscript which is in press in Biochemical
and Biophysical Research Cosmunications to include the results on
degeneracy.  Also included are the nucleotide compositions of
coding units corresponding to two additional amino acids.

  We tested the ability of many preparations of poly C to
stimulate proline incorporation.  About six preparations gave
a 5- to lO-fold stimulation; three preparations gave a 75- to 1000
fold stimulation, and four or five preparations did not stimulate
proline incorporation.  We have also found that poly CU stimulates
proline incorporation effectively, more so than pely C. When =
analyaed the base ratios of our polynucleotides, we could not
find traces of uridylic acid in poly C. Since we now know that
the code is partially degenerate, it seems likely that both poly CU
and poly C will code for proline and that this is another example
of degeneracy.  Probably an g. wli coding unit corresponding to
proline would contain both U 47

  I haven't seen the English newspapers but the American press
has been saying that this type of wrk may result in (1) the
cure of cancer and allied dissaaes (2) the cause of canoer qd
. .


Dr. P. H. C. Crick

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the end of mankind, and (3) a better knowledge of the molecular
structure of God.  Mall, it's all in a day's work.

               Sincerely yours,

Marshall W. lirenberg

m:lh