UNIVERSITY of PENNSYLVANIA

PHILADELPHIA 4

The School of Medicine

| ~
DEPARTMENT OF DERMATOLOGY AND SyPHILOLOGY June 9, 1952
AND
DEPARTMENT OF MICROBIOLOGY

Epwarp D. DeLamarer, M.D.
Research Professor

Dr. Joshua Lederberg
Department of Genetics
College of Agriculture

The University of Wisconsin
Madison 6, Wis.

Dear Josh:

Thanks for your letter of May 21 and the preparation of
K-12, I am delichted to hear that you are "morally convinced
of mitosis", I have studied your slide which is excellent,
and in which we have had no difficulty in demonstrating various
mitotic stages. In comparable material of our own we recently
have developed a modification of our technique in which the
cells are crushed, and in these it appears to be possible to
completely characterize the three chromosomes. We feel that
there are three haploid chromosomes in Kel2, and you apparently
have seen Similar numbers. I think that the odd forms that
you note containing more than three granules probably represent
anaphase stages of separation of the sister chromosomes,

We have submitted titles to be presented before the Genetics
Society at Cornell in September on demonstration of mitosis in
Escherichia coli, and further studies on the prophase chromo-
somes of Bacillus megatherium. I would greatly appreciate your
permission to include in this work some vhotographs from the
preparation which you so kindly sent us.

 

Concerning the tetrazolium, we agree that the granule is
probably a localized deposit and not a stain. We have had the
same experience with the reddish tetrazoles as you have, and
we are not entirely satisfied with them. I wonder whether you
could not use a very dilute solution of methylene blue as the tag
you require.

Thanks for the reprints. Best personal regards to your
good wife, Zinder and the others. Zinder's paper is not only
beautiful, but was well received in Boston,

As ever,

g ad D. DeLamater, HM. D.
ELD/a j Resparch Professor