MASSACHUSETTS INSTITUTE OF TECHNOLOGY
DEPARTMENT OF BIOLOGY
CAMBRIDGE 39, MASSACHUSETTS

May 6, 1958

Professor Joshua Lederberg
Genetics Building

The University of Wisconsin
Madison 6, Wisconsin

Dear Josh:

In answer to your letter concerning people in biochemical
genetics, I can only but agree with you that the problem is difficult. I
am sure that all of the names I could suggest would be obvious to you,
and you have already thought of them. It seems to me that Ernst Freese
is one of the most promising people in this area. You have probably
seen his work with Seymour Benzer on the distribution of mutations
induced by bromo uracil. It seems to me that this is one of the most
important papers on the question of the nature of the mutation process
which has come out ina long time. Freese is now continuing on this
problem at Harvard and has found that 2-amino purine is a mutagen
and has a mutagenic spectrum which is different from both the spontan-
eous and the bromo uracil induced spectrum. He has recently been
involved in the biochemistry of 2-amino purine and is handling the pro-
blem in what is an apparently extremely competent way.

As you probably know, Freese received his training as a
physicist; and it has only been in the recent past that he has gotten
involved in biochemistry. His contact with genetics at Cal Tech is
considerably longer. However, he has obviously taken the problem
of learning biochemistry very seriously and now considers it as his
major problem to understand the chemical processes involved in
mutations. Freese seems to be extremely competent. He is bright
and is interested in many areas of biology. I can recommend him
to you very highly.

— I hope that we can get together some time in the near future.
If there is any possibility of your being in the East, please let me
Professor Joshua Lederberg 2 May 6, 1958

know. Alan Garen and I seem to be in the position where we will be
able to get some results on the question of genetic control of enzyme
molecules in coli in the fairly near future.

Very sincerely yours,

-

x

Cyrus Levinthal

CL: gl