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ut ‘Be mard D. Davis

. ever of-e-“stintulating” effect-of ancther-strain ia-producing-F..A.—-- —~---. - ~~;

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New York 21, New York

Dear Dr: Davis:

eee ee Pe Bere
ington for Christmas. Perkpps you de not know that for a year
and a half I have been the geneticist with the Bivision of Biology
and Medicine of the Atomic Energy Commission. Therefore, par-
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going on actively, and I think we are getting closer to a common
ground with Zinder and Lederberg.

RO et oe ee ee ee) “
Zinder's Jour. Bact. article was rot out, and we were unaware -
that there were serious differences between our techniques and oy
theirs. For instance, our strain which furnishes F.A. is lyso- ;
genic, and the recipient is sot. Also we have mp evidence wimt- ¥

from this strain. It appears to be a dircet effect invelved with
the lysogenesis.

OW MEE Om Rm mOC me gL
in technique had any effect on the results, we have been repeating
on an increased scale the tests of last spring reported in our -
paper. In this series we are checking somewhat more carefully —
the amino acids used and are retesting every isolated strain af-
ter successive transplants. We have done the same with some of
the recombinants found last spring. This study is not yet com-
pleted, but we have already found that certain strains have changed.
Specifically, there is ne longer a gingle case remaining re Lt]
  
  

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oe De. Bernard D. Davis oo RTs er eh

  

F.A. has "carried" a requirement of the strain from which it was derived.
Ik only causes reversion of one or several requirements to the wild 1940
Thus, we still get prototrophs from 1159 strain, requiring arginine,
methionone, and aspartic acid, and also strains requiring two of these.
Nevertheless, this strain did originally appear as a single step niutation.

   
  
    
   
  
 
    
   
   
   
 
 

I am sure you will see that I am just in the midst of revision
of my ideas on this study, so it will be better for me to hold the strains
until I can be sure of my own settled interpretations. Then, I shall be
glad te send them along to you or to Lederberg directly if he wishes. Of

Ns me es Bea Oe ea ml tee tag 1.) Aa.) | ernie
make such a re-test unnecessary. ; :

At present I consider Zinder and Lederberg's interpretation
of the phenomena unacceptable on two points:

1) Our erie) are negative in respect to a stimulating effect
of another strain in Naa F.A.

2) I question on several grounds the idea that only one
"character" at a time can be transduced.

bs aa NAC ae MOM DO meme ta UT SRL Mie ers utmost oh ait ee
tion of hig over-all view is worth something.

I enclose our paper, along with a note which we sent to
a "Microbial Genetics Bulletin". Would you send me your two recent pa-
pers on Aromatic Biosynthesis.

Sometime I must stop in New York and talk these questions

eee ee OVO With you,

With kind regards, I am

Sythe