October 3, 1950.

Dr. EK, L. tatan, : . a
Dept. Biology, | 7 IA O
Stanford University, A he

California. . 4
Dear Ed:

Esther and I are both very sorry that we did not have an opportunity
to visit with you again during the sunmer, but our few weeks in Berkeley I
proved to be ail too short to do all the things that we had hoped. We j
reached Berkeley several days before the beginning of the second summer | |
session, which gave us an opportunity to see something of northern Galifor~
nia. e visited Dohzhansky at his sunmer station ab Mather (via a one-way
mountain road in and out of Yosemite), and then drove northwards to Lassen
Park, which we greatly enjoyed for a couple of days. “e returned to Berkeley
via Eureka, the Redwood Highway, and Napa valley. The course itself was
moderately successful? at least the stadents refused to believe everything
that I tried to tell then. I managed to do a very little research with
Stanler on UV effects of adaptation in Pseudomonas. As one night expect
UV strongly inhibits adaptation, but not the adapted enzymes. The inhibition
can be photo-reversed, which suggests that photoreactivation 4s not the
interruption of a process leading to killing, sut an actual reversal of
the photoahemically terminal event, There ia not a great deal of difference
between these notions, but Novick and “zilard had been thinking more or less
in terms of a poison, which could be destroyed by light before it had reacted
with the cell constituents. The greatest use of thse findings may be as a
better means of distinguishing adaptation thatn by slight differences in
the shapes of curves of 0,/time, As I had anticipated, 1t turns out that
unadapted cells also co small amounts ( a few %) of the oxidative
enzymes usually regarded as adaptive.

The main noint of this letter is to ask you about the progress of the
organization of the Neurospora map, and to ask whether you would be kind
enough to send a few stocks. James Crow and his student, Jean Pierle, have
now gone through most of the preliminaries, and would like to start building
up multiple marker stocks for crossover studies. From what I knew, I thought
that the following markers would be most appropriate (on the sex chromosome):
/o/3/xo

leuc- 47313

A/a

lys or citr (stock #77?)
centromere

ad-p =. 35203

meth 35809

albino 15300
lys 4545.

It will probably take several months at least to build up the stocks, but

bg doing them in blocks, and building two stocks in alternation 1t should

not be impossible. We would also like to use a centromere marker for another
chromosome, as a check on slippage: i.e., an ascus showing apparent second-
division segregation for the second centromere marker would be treated with
suspicion as a possible slippage of nuclei IT and ITI after meiosis. I don't

have enough information to know what best to use, but thought at least to

try 51602 (B2-temp). Would ka you send this also, if not suggestions on something
better to use?

Jim and I will very mich appreciate any help you can give us, and we will
certainly keep you informed.

The Columbus meetings were interesting, but exhausting. Conspicuously
good papers- Stadler, Darlington (the devil itself), and Ephrussi. Beadle
gave a rather surprising talk: he discussed the historical origins of the
"one-to-one" theory, and referred repeatedly to the one gene-one function € !)
hypothesis.

Latarjet wrote that he is on the hunt for possible traces in Paris of
coli Cl and C2, but refused to offer ang encouragement. ine Sphrussis will be
here in a day or two, and I'll ask them as wel] - but they will undoubtedly
be heading westward theuaselves.

Enough for now——

Sincerely,

Joshua ~ederba bg