daly 31, 1946.

Dr. E Le Tatum 2 , 1
Yale Univéreity oo ;
New Haven, Connecticut

Dear Fat

I have just talked to Mary about morphological types
that ocour in wild type strains, In our mistard gas controls
we didn't get any, but in some of the other croeses involving
wild types they have come out, Particularly non-conidial types.

1 am sure that the only way you can take care of
this is to be sure that you started with wild tyre straine that
are known to be free from all morphological types.

As for the frequency of cystine and methionine mutants,
Norm and the other peorle found about 60% of the biochemical
mutants from mustard gas treatment belong in thie category.
This le probably about the same es the frequency in A-ray or
ultraviolet material. Incidentally, Dave should have all of
the quantitative data on the mustard gas mutante.

It is certainly true that biochemicals are not frequent
dn untreated material, however some have occurred. For example,
Mary found two in B-6 mutants, one was & oystine-methionina type
and the other was the yeast extract mutant. These certainly
were not originally preeent in the B-é matant decause tha mutants
4n which they occurred were not pure for then.

Mary would like to try the adenine purple mutant if you |
would care to send it. It ts probably the came as the cnes we
already have since all of the purple ones so. far seem abut the
same, but wtill it would be good to have a direct test of it.

Things are beginning to straighten out here and most
of the people are in a good position to get to work now, | am

not quite as fortunate, but I hope to be soon, i?
. SS ne
~. ht - as
with best regards to you and the Bonners and others, | < ae
I am < 8

-*

Sincerely yours,

a

G. wv. Beadle

 

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