LAMLLAVIbGe Nee AUDL.

lith March, 1952.

Dr. J. Lederberg,
Department of Genetics,
thiversity of Wisconsin,

MADISON 6, WIS. U.S.A.

Dear Dr. Lederberg,

Thank you very much for your letter and also
for the copy of Papers in Microbial Geneties. -I found both
of great interest. : °

I am back at work again on the influenza virus
recombination story. The results in the mouse’ brain standard
experiment are quite reproducible but I find it difficult to
devise anything like a proper genetic approach to the problem,
The gist of the situation is that one arranges conditions so
that one possible recombinant will eventually emerge after |
running the gauntlet of a highly selective environment designed
to inhibit the reappearance of either parent strain. I cannot
see any hopeful way of obtaining anything equivalent to the —
whole progeny arising from a mixedly infected cell. I shall
keep on with a variety of experiments in the hope that an
approach will turn up.

I am still hoping that one day or another I
shall find an opportunity of spending some time at Wisconsin.

With kind regards,

Yours sincerely,

(F. M. Burnet)
DIRECTOR