UNIVERSITY of PENNSYLVANIA
PHILADELPHIA 4

The School of Medicine 609 Maloney Clinic
6 December 1957

THe Evpripcz Reeves JOHNSON
Founpation ror MepicaL Puysics

Dear Joshua;

Thank you for your letter of Nov. 25 and the
proof-copy of your paper on sibling recombinants
which I take it will appear in J. Bact.

Of the 18 pairs we studied, one failed to give
a viable F- exconjugant and three failed to yield
a viable Hfr. Using motility as a marker, together
with the conventional markers, 13 of the exconju-
gants geve recombinants and the maximum number of
recombinants obtained from any exconjugant was six.
In addition there were recombinants for morphology
and degree of clumping which were difficult to
score. In all but threene pedigreesg,the Hfr seemed
to divide normally, but the F- had difficulties and
produced dead bacteria in all but one completely
sterile couple. We did no F+ x F+ crosses,

Thus, except for the degree of fertility, our
data are in very good accord.

Do you have a spare copy of "Linear Inheritance
in Transductional Clones?" If so, I'd appreciate a
copy.

With best regards to you and to Usther,

Sincerely,
—_—O

LO

Thomas F, Anderson