July 7, 1953

Dear Luca:

I had promised not to distract you unnecessarily from your Congress
tasks, but I would like to ask the favor of returning a culture of W-583,
as the one we have saved is misbehaving (especially pp” ).

I hope all is well with you. Have you made any start about finding
support to visit us here? I am not sure that next summer would be the
best possible time; it would depend on whether we will have completed
re-modelling our small laboratory by that time. But it would be best to
be prepared beforehand. Are you sure that you would only be able to male
such a trip during the summer? Our laboratory is extremely uncomfortable
on hot days, and it would be difficult to get any work done. Our budgetary
situation is very encouraging now, and I have no doubt of underwriting a salary
for you (possibly up to $400 per month) which would allow a comfortable support
for you and your family, independently of any other support. The main problem
would be to undewwrite your travel expense.

Have you received the filter?

Esther and I did not make the trip to the CSH symposium; there was one person
from our laboratory (Dr. Skaar) so I can make only a second hand report. As
might be expected in a virus sympostum, there was no acute interest in E. coli
recombination. I gather that Hayes did not entirely clarify the points at issue
among us (indeed what are they!), though Jim Watson finally repppnded (to a
direct question) that pre- vs. post—- elimination was probably the only important
one. Such a fine point (and difficult to settle) seems hardly worth any fuss.
Both Hayes and Watson have written that they will visit us here during September,
so we will probably have an opportunity to review any questions in the atmosphere
of the laboratory rather than the Symposium,

As I promised, I have gone back to coli work directly. Tom (Nelson) has accumlated
a considerable mass of diploids from Het F+ Lac+ Mal-~ M- X F- Lac~ TL-ST, con-
firming previous results very nisely: all ate hemizygous for Mal, ahout 85%
Mal+S™, 13% Mal-S5, 26 Mal-S® and a few Mal+S™. There is no possibility of polarity
reversal. We are now studying the cross reversed with respect to F, and also the
elimination pattern of the Gal-Lp segment which is often also deficient, possibly
indepently of Mal-S. Zp(/ I have been occupied with diploid x haploid crosses. The
results are consistent with elimination from the F+ side, but do not distinguddh
the pre— and post—zygotic alternatives. Most of the progeny are diploid
(including the case 2nF+ x F- 1n) and do not show deficiency for Mal-S3, so
that the diploid F+ gamete mst carry at least one full complement (inclu-
ding Lac and Mal) and at least enough of a second to ensure that the
zygotes will split off diploid segregants. The eliminated chromosome is usu-
ally not recovered even among diploid progeny: if the triploid zygote
carries one chromosome which later eliminates, there may be a selective
segregation 2 intact: 1 eliminated. These axperiments are terribly cumber-

some, and not as informative as I would hope. I have also dusted the
microscope, but this is a type of work from which I ameasily distracted.

Yours,

Joshua Lederberg