October 22, 1954

Dr. Mary 8. Ut4W.l
Kerckhoff Leboratcwfas
C&i.ifor nia Xwtitute of Tsohnology
Pa6adana br GUfornia

Dear Dr, Mitehall:

Sinue 1953, we have been follolring Jrour reports on poky Neuroapora
with enthusiastic: irrterest, bnt from the distance of so-what unrelated
work. More recently, we have etarted e~mb genetb studies of yeast, spe-
uifioa3.l~ conoernLng thm aegregaticm of cytopla~nnic factors from the
diicaryophaae.  I thought that ev~tually a cromparison with kumspora
might be fruitful, and I womlered if you would send m a strain or two
Of pow fOX' thfa pU'pO80.

Your first paper (1952) on poky already nrsntioned some atbmptrr at
heterokaryon analgsla. Blaturally, differential. segregation of nuclei and
cytaplaem frost a heterokaryxm wauld help a great deal tc round out the
pi&are you have already developed, not tr> suggest any reservations on ths
intWpZWt&iOn ah!Md$ secumd frOm aBCU8 -8i.e. ThiiJ i8 e88Wltlally
what we are p3.annbg for yeast.  WOtid you aqy your own earli4r triala
on heterokargom werb the last word?  iba our yeast work gets along, we
might like to repeat them Path various d%ffereat design8 to crop with
different possibXl.fUes of interaction of nuulei and llpoky cytopla@' o

fmxld be grateful tiy~uforgand~aulturee of thsmatmaalpoky,
You would &eo save ua additional wOrk if ~rou could furnish poky &n 00&i-
nation with albino or with an auxotmphic mutant of soae emrt, preferably
but not DSCe888r~ ~entromre-lInked.

Esther sends her best; Iara sorry never tQ have had theopportunity
of meeting you Iqm?Jlf.

Yours aincmaly,

Joehua Lederberg
h'Of~8SOr Of &E30tiOS