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PROFESSOR R. A. FISHER, Sc.D., F.R.S.

MISS M.F.LSPEYER, B.Sc.
Research Assistant and Secretary

UNIVERSITY OF CAMBRIDGE
DEPARTMENT OF GENETICS

WHITTINGEHAME LODGE
44 STOREY’S WAY

CAMBRIDGE
Tei. 55822

18/3/L9
_ Dear Dr. Lederberg,

I am sorry you did not hear from me sinee I
had your strains; but the only thing I could do at that time was,
as I wrote you then, to test whether they were still alive.

Only since the beginning of February Youla
start some work, end that has allowed me to see that they do
behave as exvected also undé~ the other points of view. At&this .
very first steno of my work I have but little to tell you; but
I should like to ask you some suscestions.

1}: the frequency of recombination in .
the three experiments I have made was rather constantly a
prototrorhs ver cell of each of Ithe two strains. I an following
rather closely the technioue you give in your 1¢&% paper én
Genetics, except that my cultures are unshaken,and I mm not
using so far the trace element solution. Do you get consisten-
tly higher frequencies than that,and did you find recently
any means of increasing considerably the frequency of recombi-
nation or mating ? I adndt like to use the UV technique propo-
sed by Stone and others hecause it might affect cpossing-ever.
94: I am not completely s@tisfied with
the EMB technioue of scoring for lactose fermentation. The
difference between W 583 gnd 58-161 seems more one of time
of fermentation, and at any rate 58-161 seems a poor fermenter

by that technique,in comparison with coli B.

 
rae

Lobel le

OAD
I did not test so far the other sugars for lack of reliahle sugers=
; : \ Tbe nth A 9 te a .
chemicals, WH # yor tke F fo as t “1 t

fermentelon 7.
. 3): W 383 seems resistant not only to

Tz, but to Tg as we@l . IT must test tT, however, before maxing a defini-

te Statement, because it is a rather old stre ‘in of ViTUS » But you pro-
bably know Ww more about it. |

oo Oo BD: T am | woricing at 30° C. as a suggest,
but I -m feeling rather nostaigic about the ‘usual 37°C. Is there any

special reason, ‘for working at 30° 2

My ‘plen-is essentia-ly. to secure new biochemical mutants in
these stocks, and to stucy ‘the pattern of virus resistance of coli
“K-12 . 1 want to have a fair samplé of genes over all the chromosome(s}

length. a
I should be very interested to know more about your divioid
strains. Ahd I wish. to take this oppostunity to ask you a reprint ©
of your“very good review’ "iicrobial genetics".
“With best thanks,
“Yours sincerely

. Cage cet