Mee

July 7, 1955

Dr. T. C. Nelson
Institute of Microblology
Rutgers University

New Brunswick, N.J.

Dear Tom:
Thank you for the postcard notes.

I think the myséery is cleared up. I had been concerned why both

Esther and I had dAvariably gotten G. hemizygotes while you had heterozygotes.
Our individual results were too consistent to explain this by variability in
elimination pattern.

It tums out that W-2406 was mixed, and consisted about 50% (or more) of a
Gal-slpw type. (At least the culture now in stab looks this way). The apparent
Gal, heterozygotes are actually not segregating Gal,-, but this slow-fermen ting
type, which looks quite different from - when compared side by side on

EMB Gal. This slow fermenter is also Galy+ by transduction tests. So 1t would
appear that your crosses were actually:

Het Gal,,* Gal,- x Gal, Gal,+ to give three kinds of diploids:
a b . c
Gal_,+ Gals +/~ Gal,+ Gale +/+ and Gal,- Gale +/~

The aatter corresponds to your two G. "homozygotes"—~ they revert to give a
Stock which is segregating Gals, not a‘'full Gal-/ ‘he full Gal+ diploids are (b)
and most of the heterozygous diploids are (a).

We are now concerned to try to verify again that gal, 1s not dech&tving us, i.e.,
to be sure that so called Gal, heterosygotes are really segregating Gal, +and Gal ~

since Gal, now remains as the only Gal which is not eliminate. Transduction tests
should help to verify this point.

Za I am still confuded about #269. Your postcard said that this was W2593 x
Wel324; your notes gave 269 as W-2251 x Wel324. Is either or both correct?

Yours sincerely,