THE UNIVERSITY OF WISCONSIN
     COLLEGE OF AGRICULTURE

Madison 6

DEPARTMENT OF GENETICS

November 12, 1948.

Dr. Barhara WClbtock.
Dept. of Genetics,
Carnegie Institution,
Cold Spring Harbor, L.I., N.Y.

I have just received your letter and scheme for the coli heterozygota.

I haven't studied it yet indetail, but I ha$bn to thank you for the effort

that you must have put into it. I will certainly study it very thoroughly.

Unfortunately, I think that I may have misled you concerning one of the

premises2 11-3. "the type of crossover chromatids recovered in the the segre-

gants are not the expected ones in that many unusual multiple crossover

chromatids are represented, tk I did emphasize that csrtain multiple-mutant types
                              e-s

could be recovered from the heterozygotes,. but they are elusive&with respect
to the techniques that were previously available, viz. selection for prototrophs.

In fact, the multiple mutant types are merely the complements of the prototrophs,

techniques for the recovery of which had been worked out before. This restatement

does not,1 think, alter the bases of your suggestions, but may require a somewhat

simpler veri&on.

Again, I want to thank you for your suggestions,
                             and remain,