April 26.1949
Dear Max,
Some hurried answers while I check the cultures you sent.

I don't know of any good way to accelerate segregation. My main
troubles had been the reverse. I did do one experiment with the addition
to broth of 4% sodium nucleate with promising results. It might be
worth trying.

H-168 4s probably hemisygous for Mal-, heterozygous Ara - # . But
the Ara marker isn't worth much, and I would ighore it. I'm still bugy
trying to develop stocks which may have more clearcut markers, more
suitably spaced, than the rather difficult Gal- and Ara mutations in 168.

Mtl~ ie reasonably stable. I have picked up some suppressors which
are a very weak#. I would say that Xylose would give the very hest scoring.

The parente and constitution of H-72 are correctly given,

You've put down the parentage of H168 correctly; I'm not sure that
the chromosomal arrangegent is the same. To account for homosygous loci
with heterozygous parents, $here aust be crossing over before the propa~
gation of the diploid as well as after. I have tried to find more than
one kind of heterozygote in the initial protrophs from which they are
obtained, but without success. Arguing from the data which I sent you
last time, I would say that the arrangement is probably:

x ye ~~ re
uO . oF Se Tat L.
although the #'s are all coupled in the parents.

That is, there mist have been a crossover between Kyl and Gal
between the fueion and the proliferation of the heterozygote. The other
stran@s presumably segregated out, and unless prototrophic, were lost.

 

 

Do you expest to go to Cinncinnati? It seema about time for a long
talk. All I wanted to say about your single-cell work was to cite your
pedigrews as proof that the heterozygotes and mosaic colonies do issue
from single cells.

I'll write again in about a week.
Sincerely,