December 6, 1951

Dr. Henry J. Vogel
Tbe Res Lab

411 E, 69 Street
New York 21, N.Y.

Dear Dr. Vogel:

In answer to your letter of the 5th, I must admit that I have
never had a penicillin-resistant mutant of K-12 (for not having
looked) (E. coli), and therefore can not answer your question about
its possible dominance.

I am, howeverg very much interested in the dominance relationships
of drug-resistance. If you would care to send me a penicillin-resistant
mutant in either the B-M~ or T-L-B,- auxotroph lines of E. coli K-12,
I would be glad tp try to put it ito a heterozygote and test. It would
not matter too guch if the resistant mtant were a single— or multi-step,
so long as it could be easily different&ated ffom the parent sensitive.
If you can provide such a mutant then, I would also appreciate your speci-
fications on its behavior.

a

Yours sincerely,

Joshua Lederberg

PS. I'll give you 2:1 that the resistance is recessive.