or neither*

Department of Genetics, University of Wisconsin, Madison 6, Wis.

January 7, 1951

Dear Dr. Hayes:

Your interesting note of the 31st Dec. has just been received.
I hasten to reply to a particular suggestion, which has not escaped
us, and has been submitted several times previously: the relation-
ship of lambda to recombination.

When we first discovered that K-12 was lysogmic, ay wife's first
thought was to determine what relationship, if any, this might have
to the sexual. process. Disinfected cultures (both sensitive and immune )
Were obvaansd in complementary cultures, and these proved to cross
quite wali, wiebher ox not sither#or botn parents carried lambda.
we are especially interested in this point because of the very close
relationship of piugs to recombination in Salmonella. In Salmonella,
however, the "“gamute” has very different propertiss, both genetically,
and imsuvar ag ib is filtrablv, Zrom that of Z. coli 5-12. We have not
been. able to detect any “genetic” propecties in flitratos op lysites,
axcepy Yor Laubda iuseii, aaa tnis is a crucial test of any identifi-
Cation cf lambda wita a gaetic function.

Oa the other hand, the stimulation of recombination by UV may very
weil be aediated by the activation of iatent virus, in sone gacondary
Way, and these observatiogs deserve very spibical aitention. Ye have
been working iately on some of tha details of UE-activation, anid plan
to compare the effects of LV re recoabinatioa on lasds-sensitive and
aysugenic cultures.

Zatween 3008 observations that Cavalli hes written se, and soms of
our owa, it may be possible te conclude that (-.77 end soa of its
ancestors carry a self-incompatibility factor. As far as I know, this
factor is nov shared by any of the stocks in your possession tht could
be crossed with W-li77, but we even to have picked up the same factor
again in some B-W- stocks. The picture is pretty aurky, und wo are
trying to work it out. Tt does mot lock as if this should have any
direct bearing on your finaings, but i thought you inight want to keep
it in mind.

To return to lambda again, I should point out that although a few
of the strains that cross with K-12 are lambde-sensitive, the majority
are not. For a few of the strains, we have inter-cresses, and crosses
with "disinfected" K-12 lines which are quite successfil in the absence
of any indication of lysogenicity. You ars free, if you wish, to postu-
late additional latent viruses for which we haves ao sensitive indicator,
and which do not show UV-activation of lysis, but for this purpose,
such an aemmption seems to me rather ad hoc.

Yours sincerely,

Joshua Lederberg