UNIVERSITY OF CALIFORNIA

VIRUS LABORATORY
BERKELEY 4, CALIFORNIA

June 11, 1959

Dr. J. Lederberg
Stdford University
Stainford, Calif.

Dear Dr. Lederberg:

We now have converted your lac-deletion
mutant ( W4032) from Hfr to F” by
mating it with an F” that seems wild-
type in the lac region and selecting
M-P-lac” S* recombinants. We then» ¢~)
viated a Hfr lactinducible with it(Sna
found that the F” acted like a constitutive
strain( that is,upon entry of the lac*

locus in the absence of inducer there ~%
was a copious production of $-gal- >
actosidase which stopped after about S
70 min more). It taerefore seems that &

if the strain from whichwW03z was te
derived was inducible the mutation must »
have changed it to cogtitutive. this -

is the result 1 would hope for from -

a deletion, since our earlier results
show the constitutive allele to be
the passive ( recessive) one.

would you be kind enough to send me
the pedigree of the strain from which #
4032 was derived, now it was obtained,
and what evidence you have for its
being a deletion?

iy apologies for having to trouble you;
However 1 no ve the above information is a 3
small compensation.

Sincerely,

OD

Arthur B. tardee

ere RARER ERR E RNR