Aprdil 4, 1950.

Dr. J. Me Bonner,
Yale OBL
New Haven, Conn.

Dear Dave:

I am very clad to hear what progress you are making~ the beneficent
stimulation by Stadler could certainly have been predicted. Give hin
our best.

It is certainly weloome to hear about some real genetic work being
done on Neurospora. Has cnoush groundwork been laid sco thet you Imov
what linked factors to use to check the correlation of tho nics mutation
with oroseingover? I've had a somewhat analogous situation in coli:
Lac, and Lac,- orossover considerably less than 0.1% However, they yield
a Lacf diploid heterozygote. In seneral, they oan aleo be distincuishad
by tielr action on butyl galactoside. But at first sicht, they were regarded
a8 allelic. There ia one point on heterokaryons that I have been a
little fuhatical about: were your tests necative because of the ineffeo-~
tiveness of a heterckeryon, or was no heterokaryon forme?! I have always
felt that Independent evidence (viz. other markers) should be brought up
for actual heterekargon fornation whenever this ie critiosn!.

There is one other problem that may now be possible to attack in
Jeurospora. A great mmy other fuhéi show evidence, more or less secure,
for delayed reduction, occasionally resulting in diploid mycelia. Using
closely linked factors, which should interact to give the wild type in
a double heterozygote, one should be able to select more or lese effectively
for such exceptions. Comparison of tipkeédaxnad heterokaryons prould really
be an interesting problen. with heterocsypotes.
I bring thie up only as an analogy to the cold diploids.

If I an not wistaken, Ram Stadler is pretty much of the same mind as
we aro on gene-enuyme relationships. vould 44+ be toc umrieldy for 211 three
of vs to join forces?

Sineercly,

Josie Lederberg