Biological Laboratory
Cold Spring Harbor
Long Island, New York
August 20, 1946

Prof. J.B.S. Haldane, F.R.S.
Dept. Genetics

University College

London

Dear Haldane:

I am sorry that I have delayed so long writing this letter,
and have been keeping your manuscript. When I came back there
was here first the symposium and then a phage course for three
weeks, and neither left sufficient leisure time. The symposium
was very exciting, as you may have heard. A number of people thought
they had indications of sex life in bacteria. If bacteria have
sex it is entirely reasonable that it should be discovered now
since now for the first time people are doing experiments with
genetically marked strains. The most exciting experiments
were some done at Yale in Tatums laboratory by a young fellow Leder-
berg. He first secured two double double mutants of a strain of E.coli
(X-ray induced). Each of the double mutants had two growth
factor deficiencies. One mutant was deficient for A and B, say,
and the other for C and D. Then he grew these two mutants to-
gether in broth. Then he plated the mixture out on basal medium
and obtained a few "prototrophs" i.e. colonies of bacteria re-
quiring no growth factor. He seemed to have done most of
the obvious control experiments. He has since tried to do the
same thing with our strain "B". He did secure two double ce-
ficient mutants, but did not get any prototrophs when growing
them together.

Luria has been trying to do a similar experiment with mu-
tants of the phage resistance type. He takes, say, B/1/2 and
B/3/4 and grows them together and then tests to see whether he
has any B/1/2/3/4. So far no luck.

With best regards

sincerely yours

M.Delbruck

JUL 22 1974 *

This excerpt is taken from a letter commenting
on a ms. on the statistical theory of mutation by Haldane
that I had borrowed (?from Delibruck) and had photocopied.
Most of the letter concerned detailed mathematics. I
assumed this material was left with it by inadvertence.

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Sake

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