Wovember 16, 1953

Miss Ethelyn R. Lively
Department of Bacter tology
University of Illinois
Urbena, Tllinois

Dear Ethelyn:

Before you find yourself too deeply preoccupied with Thanksgiving turkey
(which I hope you will enjoy as much as ever), could you do me a favor?

I am getting back now to single-cell and cytological studies of Hfr x F-
matings, with some interesting results. I am surp#ised to see now that I have
for a long tio overlaoked some of the implications of the already available
data on the mechanism of this mating, at least vis-a-vis the Watson@Hayes
pawtial gamete theory. From some of these crosses, colonies could be recovered
which contained not only recombinants (usually detected as Lac+S™) but also
both parents (Lac+S® as well as Lac~S!). The question still has to be settled
whether such synkaryon colonies do actually issue from single cells, a point I
am reviewing right now.

At any rate, your own data on single cell isolations of W-1895 x W-1956
would be velevant ani should be included in the final tabulations. As best I
ean real your notes, I infer that most of the almgle cell clones were, unfor-
tanately olated dirsctly on FMB Lac em agar, to detect recombinants, so that
the persistence of the Lact 8° (Hfr) parent would not be revealed. However, I
have a distinct recollection @@ an experiment in which only the two parents
were recovered from a single cell, presumably from a plating on FMB Lac without sm
Could this have been your experiment 7/15/52? I could find no record that the
Lac+ components were actually tested with sm and found to be 88, though your
tabulation would imply that they were.

I wuld appreciate it if you could review the notes that I am enclosing
to summarize the results with the following information on each experiment:
A) Character of cross: presumbly W-1895 x ¥~-1956, but any treatments, 1277
8) Medium of initial plating of clone (+ or ~ sm), ©) Incidence of Lac+, Lac-
and, where relevant, their S character. Did you save any of these isclates?
I could not fini them in the frig', though your H-267 segregants are still here.

A good part of the fruits of your labors here is beginning to make sense,
and it would be wise to consolidate them to the visw of eventual publication.
If you have the occasion or opportunity to visit Madison again for a day or
two, I would like to be able to review these notes with you ac that the infor-
mation is not lost. We can probably arrange to pay any extra-ordinary expenses.
Seymour is driving up for Thanksgiving you might return these notes with
him, if they are ready. If you can decide sooner about the 7/15 result, I'd like

to hear about it. With, best wishes,

Joshua Lederberg