NEW YORK STATE COLLEGE OF AGRICULTURE
CORNELL UNIVERSITY

ITHACA, NEW. YORK

 

LABORATORY OF BACTERIOLOGY

April 26, 1949

Dr. Joshua Lederberg
Department of Genetics
University of Wisconsin
- Madison 6, Wisconsin

Dear Josh:

Enclosed are a couple more pedigrees from H168 I was a little suspicious
of the small one so did not want to invest the time necessary to carry it any
farther. The original cell proved to be a heterozygote so it would have been
ali right. The sors 5 cultures 2 ge Ln re the most extensive group yet
and I intend to carry’them out thid¢’fa oping that the segregation will
occur early enough that we can perhaps account for the possible inviable
nucleus. This series 5 case,cultures 239 and 240 with the inviable 5-120,would
be interesting if we did not already have several observations indicating that
the sib call to a segregant is a viable heterozygote.

I am also sending out the following cultures from the 5 series:
203, 204, 195, 196, 25, 53, 54

just on the chance that they may be valuableyalthough I think probably all
of them are heterozygotes. I am checking them here further but I think it
is best to get them to you as quickly as possible. I am dumping same of the
original broth culture into some melted agar to attempt to cut down the
amount of growth before the cultures get to you.

I am not planning on giving anything at Cincimati. I you wish to use
any of the stuff we have so far you are welcome to do so, Actually, there is
not a great deal to say beyond the indication that the mechanism is more com-
plex than one might have hoped for. I hope to have several more pedigrees
as extensive as this series 5 before the Cincinnati meetings

Have you played around with cold shocks or any other mechanism for increas-
ing the frequency of the segregation? It would be a big help to me if there ——
were Some way of inducing the segregation to occur at a bit higher rate, ‘T

have made a few random notes on the back of the series 5 sheets which may or

may not indicate that I can spot a cell which will not grow. Actually, I

think if I were more careful I could raise my predicting ability to something

like 80 per cent accuracy. The main reason I am interested in this is that

I feel the failure of cells to grow can not be laid entirely to the rigors of

the technique and that there is an actual physiological difference which

arises before I separate the Stbse OAs to culture 2-200 I am positive that at

Qe
Dr. Joshua Lederberg Page 2 April 26, 1949

the time I plated istruly serregating heterozygous cells were present in the
culture. I will replate in an effort to confirm this. Actually I have never
classified a culture as heterozygous on the basis of its being a mixture of
+ and = cells. I raised the question earlier because it was a possibility.

What is your guess as the nature the aberrant revion? Just thet

detticiency or a deficiency se some change or is the situation so

confused that one can not make a good guess?

Does Mb1- revert readily? If so, I will switch to xylose.

Very truly yous,
M. hop
MRZ sje

Enclosure

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