May 1. 1957 .

Tear Dr. Demerec,

We have received the program of the forthcoming nucleo-
protein symposium. I reperet that we shall not be sble to attend
the entire conferefice. I also understand that it is not your
policy to accept reservations for only part of the symposium,
but my wife and I are exceedingly anxious to hear the speakers
who are scheduled for Monday and Tuesday, June 16-17. Therefore,
if you should liter find that accomodations coulc be found for
us for Sunday night through Tuesday aftermoon, we should be highly
grateful.

You may recall that I mentioned at my seminar last March that
the phage resistance pattern of K-l2 difiers from that of B in
that K/1,3,5 occurs as «a frequent type. I find, however, that dif-
ferent phage stocks are behaving differently; to clarify the situa-
tion it woulc be exceedingly helpful to have certuin bacterial
indicators. J wouls ereatly appreciate receiving the following
mutants which you mention in your papers, if available:

B/:
i 1,5 3,4 3,457 G/1/7. If you have any strains

which are resistant to T5 but sensitive to Tl, they would be par-
ticularly desirable. ve)

The micoid type of K/1 has been studied somewhat, and appears
to be the result of & highly unstable mutation, rapidly reverting
to sensitive; it has however, been crossed with sensitive striuins,
and differences in the recombination Frequencd with Lae sugzest

td u
that it is .t a different locus from the other Vy