March 30, 1°60

Or. Howard 1. Adler

Biology Division

Cak Ridge National Laboratory
Post Office Box Y

Dak Ridge, Tennessee

Dear Dr. Adler:

We have sent you an Lp? derivative of Hfr-1 (Cavalli) and a
multiple marker F stock. Each of the suger markers of the latter
should be checked for purity, and reisolation may be required.
Hifr-l is the one we have worked out best. The best source of
well mapped out, lambda-free Hfr stocks should be in Dr. Francois
Jacob's collection at the Pasteur Institute, as he has published a

series of complete maps and has tested zygotic induction in each
of them.

Sincerely yours,

Esther M. Lederberg