CARNEGIE INSTITUTION OF WASHINGTON

DEPARTMENT OF GENETICS

COLD SPRING HARBOR, LONG ISLAND, N. Y.
17 May, 1950

Dr. Joshua Lederberg
Department of Genetics
University of Wisconsin
Madison, “isconsin

Dear Joshua:

May I ask a special favor of you? We are now vreparing the
laboratory manual for the course in bacterial genetics we are
giving here this summer, and it seems to me that the paper you
wrote for Methods in Medical Research would be very hebpful.
Since the volume will come out too late to be of very much use,
T wondered if you had an extra copy of the paver, and if so,
whether you could send it to me. I could return it very soon if
necessary. We aren't sure at this point what to expect of the
course, but we have an interesting and motley crew of students,
and enough distinguished visitors to provide some highlights.
Delbruck will be around, and Hotchkiss has agreed to give a
demonstration and lecture on transformations.

Thanks, by the way, for sending your K-12 histidine-
gerine/glycineless stmein. Unfortunately, it doesn't give proto-
trophs on minimal medium. I have nearly completed the experiment
I mehtioned to you to test the suppressor hypothesis in our
material, and it is going very well. Of twenty auxotrophs
isolated from a histidine-serineless reversion on minimal supplemented
with both histidine and serine, 17 turned out to be monoauxotrohs,
and 3 require both Bistidine and serine/glycine. No such combination
has turned up in extensive controls using wild B/r, nor have T ever
heard of anyone finding khis such a mutent in a single step. It
seems to me to be pretty good evidence for the suppressor hypothesis.
What do you think?

If your summer plans include a visit to New York, we would
love to see you and Esther, and would be ready to unroll the red
carpet at any time. With best regards,

Sincerely,

Evelyn M. Witkin