CARNEGIE iNSTITUTION OF WASHINGTON

DEPARTMENT OF GENETICS

COLD SPRING HARBOR, LONG ISLAND, N.Y.

4 August, 1949

Dr. Joshua Lederberg
Department of Genetics
Umiversity of Wisconsin
Madison, Wisconsin

Dear Joshua,

Sorry your letter went so long unanswered. I
have been rather swamped since I came back to work a couple
of months ago, and anyhow, I've always been a fiasco as a
correspondant.

Being a mama is lots of fun -- our little Joey
grows and grows, and hrings us lots of joy of a brand new
type. I must confess I had some anxiety at first about
being a part time mother, but sofar at least it has been

working out wonderfully well. No signs of neglect yet
either in Joey or the little bacteria. Hope you'll come
see us when you visit N. Y.

As to the microbial genetics course, I don’t
think my outline would be of any help, as the scope and
purpose of my course Wee very different from the one you
have in mind. My course was directed primarily at
those interested in genetics, and it dealt with aspects
of the gene problem as approached through microorganisms.
Also, it was a graduate course, with prerequisites of
both genetics and bacteriology, and was given on a
rather advanced level. All this in addition to the fact
that my outline is very general makes m think it isn't
worth sending on.

I've been extremely interested, naturally, in
your heterozygotes -- is anything new? I've been hard at
work on the peculiar action o@ nucleic acid (yeast ribose)
on the frequency of phage-resistant mutants in B/r. It
is almost established now that the effect is a matter
of conversion of delayed mutations (either spontaneous
or u.v.-induced) into zero points -- in other words, nucleate
takes the place of diVision in bringing out phenotypic
expression of delayed mutants. How? I don't know yet,
but it may possibly be a segregation phenomenon, which
makes me wonder if high concentrations of sodium nucleate
might affect your recombinants. Havw you ever tried this?

Best regards to Esther, and you'll hea from me
moon on the question of the M. G. Bulletin.

Sincerely,

Colyer