CARNEGIE INSTITUTION OF WASHINGTON

DEPARTMENT OF GENETICS

COLD SPRING HARBOR, LONG ISLAND, N. Y.

January 5, 1955

Professor Joshua Lederberg
Department of Genetics

The University of Wisconsin
Madison 6, Wisconsin

Dear Joshua:

We will be very glad indeed to supply you with any of the material
from our stocks that you can use in your experiments, We have over 200
mutant strains carrying nutritional deficiencies for amino acids, purines,
and galactose; and we are now using them for studies of allelism and
linkage behavior. We are finding that similar mutants--for example, 50
cystineless, 10 tryptophaneless, 28 histidineless, ete,--can be placed
in groups, either using transduction or the study of metabolic blocks,
and that the groupings reached by these two methods coincide, You will
remember that we are interpreting this situation as an indication that
each group represents alleles (pseudoalleles) of a locus. I will be
glad to send you one representative strain of each group, or more if
you should desire, We can send you lysates, but I am wondering if it
would not be more convenient for you to have the bacterial strains so
that you can use either lysates or bacteria.

As soon as I hear from you about your preference, we will get the
material ready to be shipped to you,

With best regards,

Sincerely yours,

/ | VWQee,

MD:af M. Demerec