UnNIversiry or MINNESOTA

Tue Mepicat Scuoou
Minneapouis 14

DEPARTMENT OF BACTERIOLOGY
AND IMMUNOLOGY

September 22, 1958

Drs. Esther and J. Lederberg
Department of Genetics
University of Wisconsin
Madison 6, Wisconsin

Dear Josh and Esther:

Thank you for the greeting and letter, Esther. Dr. Sermonti would like to visit
Madison once or twice during his stay in Minneapolis. I must confess that I would like
to see you both again too. I prefer to leave here some Friday noon and make the return
Saturday night or Sunday morning. The weekend is preferable because I would like to
bring Lois and the children on at least one of these trips. Therefore, would you please
choose the weekend most convenient for you. I might suggest September 27.

Dr. Sermonti also wants to see Dr. Raper. That need not be on this trip, of course,
since we contemplate another trip to Madison later.

We have started on collaboration. We have not yet hit the critical part of the
experiments which depend on the stability of the various ''auxotrophic recombinants".
His two strains are compatible with at least 1 of mine. We are currently comparing his
standard '"'cross'! to my ''standard cross"! and then a ''cross'' employing one of his
strains and one of mine. The organisms are entirely similar I am convinced, therefore
it is the interpretations which are at variance. I do not yet accept all of his experimental
assumptions (and probably he questions some of mine) but everything is going well as of
now.

We do have the compatibility system worked out a little further with our own strains.
Remember: A+B ---- + .
B+C----+
A+ CG ---- -
Mutants which are closely related (shortly removed from the common ancestor) go best -
with one exception. The compatibility factor has not been found to be infective (in
cursory experiments).

Details can be supplied when we get together.

Hope to hear from you soon. My very best wishes to you both.

he,

S. Gaylen Bradley