October 23, 1956

DrE Borek

Dept. Bloohenistry

College of Physicians ahd Burgeons
New York 32, N.Y.

Dear Dr. Borek:

I made one trial on inducing protoplasts and it looked all right; however,
I have made no detailed study of this question & will be quite pleased
if you will. Our immediate interest with this system is the hope of
uncovering additional mechanisms of genetic transfer: so far, this has
been unrewarded, but we are pursuing the conditions of maintaining K-12
as the wall-leas "L-colonles".

The problem you doubtless have in mind should be a very attrac tive one:
one suspects that it may be possible to intervene in the steps of virus
formation more actively than is possible with intact cells. Obviously, a
great many other people are likely to share this interest. In partioplas,

I would urge you to confer with Dr, Norton Zinder at the Rockefeller Insti-
tute.

Dr. Morton succeeded in separating the H from the Lac markers in your
atrain by recombination, but they are very closely linked. Davia told us
that the Lac™ autant was obtained first, and the H- in a second step. He
no longer had the Lac™ as such, but we have just received a number of
other mtantad< besides the H” that had been obtained from that Lac” and
will test these for constitutivity before going ahead. If these are not
constitutive, we will have to obtain Lac‘constitubive recombinants as the
next step. This work has not been going as afst as I had hoped: Morton
just received an appointments as a geneticist in the medigal echool here
and 1s working 1/2-time on this research. Butvit will be pursued.

I would have been happy to have Mies Rockenbach here, but the arrangements
since made hage been very sé&isfactory.

Yours sincerely,

of ! f

2° Josma Lederberg:-~