June 16, 1969

Dr. R. K. Mortimer
Radiation Laboratory
University of California
Berkeley, California

Dear Bob:

You were away in Europe when I tried to call you, so I thought I'd speed
things up by a brief letter.

I have no intention of dabbling again in yeast genetics in any proper
sense, but I would like to include a yeast system in some tests for
chemical mutagenesis and allied phenomena. For use in just that way, I
would appreciate it very much if you can send me a diploid strain, hetero-
zygous for the pink adenine marker that would be advantageous for quanti-
tative studies for response to radiation, in this case, of course, induced
segregation. I don't know whether you recall that I had had a somewhat
similar experience with diploid E. coli quite some years ago (see the

Cold Spring Harbor Symposium for 1951). We are looking at these diploids
too, but they are spontaneously unstable to a somewhat annoying degree,
and for that reason may not be as sensitive indicators of low-level effects.

I haven't followed the story of DNA repair in yeast particularly closely.
But if there should happen to be some repair-defective mutants that could
be coupled with the adenine heterozygote, I would be particulara}ygrateful
to have the appropriate stock, together with the non-defective control.

T take it for granted that the induced segregation is some side effect of
repair of DNA leetons.

Please give me a call if any part of my request is obscure or unreasonable.

Sincerely yours,

Joshua Lederberg
Professor of Genetics

See'MMG, Spring 1969"

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