March 10, 1949.
Dear Max:
I've managed to develop a heterozygote culture suitable for detailed crossing-over studies sooner than anticipated, and am enclosing H-168. This culture has all the advantages of H-72, plus a few additional markers, so there would be no reason why it should not displace H-72 entirely. It was obtained as Lacv from the cross
B-M- Vlrc Het x T-L-B1- Lac1- Mal- Xyl- Gal- Arab- Mtl- V1r
It is definitely segregating for Lac, Mal, Xyl and Gal, but seems to be pure (hemizygous or homozygous?) for Mal-, Arab-. The "-" in reference to Galactose and arabinose means only somewhat slower than wild type; for lactose, maltose, xylose and mannitol there is a very clear differentiation. I'm checking to verify the heterozygosity of the other loci, but from other experience, Vlc, V1, M, T, and L should be heterozyous also, although with the possible exception of phage resistance (using T5 to score V1r/V1s) these factors are more troublesome to score on large numbers of segregants.
My apologies for the mathematics in my last letter--I just ran across your thesis in J.I.D. I would appreciate a set of your reprints on bacterial variation if you can spare them.
Sincerely,
Joshua Lederberg