THE INSTITUTE FOR CANCER RESEARCH
and
THE LANKENAU HOSPITAL RESEARCH INSTITUTE

7701 Burholme Avenue
Fox Chase
Philadelphia 11, Pa.

July 29,1955

Dr. Joshua Lederberg
Department of Genetics
University of Wisconsin
Madison 6, Wisconsin

Dear Joshua:

Sorry, but I cannot answer the question in your letter. We had in-
direct evidence (cell size) of aneuploidy in the abnormal embryos developing
from eges fertilized with partially inactivated sperm, but no chromosome
studies. The reasons for this were 1) we got the nuclear transfers to work,
and dropped the other project and 2) it was very hard to do good chromosome
studies on early embryos anyhow. However, recently Marie DiBerardino, who
works for Tom and me, has developed a method, for making squashes of early
embryos that gives good figures. So far we "have been using this only in the
transplantation experiments, but it would make a solution of the other problem
feasible.

If it were done I'm not sure what we would expect. Actually in any
given embryo there would probably be a variety of chromosomal complements,
and it would be very difficult to assign developmental significance to par-
ticular chromosomal conditions. However, by combining the dye type of experi-
ment with chromosomal studies and nuclear transplantations one might really
learn something. Whether each chromosome would turn out to be a unit of
response to the dye I have no idea.

Apparently there is very little of this sort of work in Drosophila.
I asked Jack Schultz and alli that he could think of that would possibly be
interesting to you was the paper by Rehmy & Fahmy in J. Genetics 52, which
you probably know anyway.

Incidentally, the methodological trick in getting good chromosome
preparations with some kind of refractory material is merely to soak the fresh
material in Ca & Mg-free Nui-Twitty solution containing 0.02 M phosphate buffer
(pH 7.5) for 15-30 min. prior to squashing in acetic orcein. The effect on the
spindle is rapidly reversed if the cells are exposed again to Ca & Mg. The same
result can be obtained with colchicine, as Hungerford here has found, but with
more fuss. I mention this just in case it might sometime be useful to you.

Best regards to both of you

  

Robert Briggs

RB: eh