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THE UNIVERSITY OF WISCONSIN
MADISON 6
DEPARTMENT OF ZOOLOGY

BIRGE HALL

March 6, 1961

Dr. J. Lederberg
Department of Genetics
School of Medicine
Stanford University
Palo Alto, California

Dear Josh:

Thank you for your note r.e. the H-ct4 thymidine effect,
Please forgive me for my laxity in not sending you reprints.

The data reported in NATURE have since been confirmed in
an additional repeat experiment. Moreover, the enhancement
effect cannot be obtained with tritiated water, suggesting
that the internal pres€ute of H7>TDN in chromosomal INA is the
critical factor. It is my guess that the effect is more
likely to be due to steric phenomena (as you suggest) than to
radiation; however, this guess is based only on the fact that
the actual number of H3 decays invélved in our experiments is
fairly small. The combined effects of H°TDN and chloramphenicol
(see enclosed B,B.A. reprint) are as easily reconciled with
a structural scheme as with a radiation damage model at our
present level of ignorance,

Your suggestion of trying D-thymidine is excellent and wn
would lead to a technically simple experiment. Do you happen oe he

to know of a convenient source of deuterated thymidine? «— 9°

I am sorry that I did not find the time to visit you at «*
Stanford last month when I spent a few days on the West Coast. pi
I hope the opportunity will arise again.

fr

( a With best regards to
We feo

 

Assoc. Prof. of Zoology

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