Hiss Marla J. Sehneider

_—
66 Zast 78th Street —; a ch
New York 21, New fork

Dear isa Schneider:

Thank you for sending ma your report, which obviously represents
a great deal of thought and care on your part.

I sense a certain amount of bewliderment on your part, but I am
not surprised. I think that mech of the confusion and apparent contra-
diction in the literature, which is reflected in your assimilation of
it, 1s simply a historical process. The information you summarized is
at the very frontier of discover, and we find out new things every day
which change some details of our thinking and help to enlarge our under-
standing. The transition from ignorance to knowledge is alwaya halting
and tentative, one step at a time here and there, and likewise it takes
time for any scientist to educate himself on current progress in every
field,

vore explicitly, I do not think there is any longer a ssrious
doubt of the occurrence of sexuality in E. coli strain K-12, and possibly
in some few other bacteria. Transduction is another mechanism, which has
4 number of different forms, and haa been discovered to occur in juite a
few organisms. Just as different organisms have evolved different
techniques of locomotion, swimming, flying, crawling, walking, these are.
different techniques of venetic recombination. And if they overlap in
distribution, well birds can walk ani I trust you can swim. ‘what we
have been describing are the occasions and limitations of these techniques
and we can only report what we find. Fortunately, it 1s not difficult to
tell experimentally when a bacterial species is using its various
techniques: in practice they are used unier different circumstances that
this causes no trouble. For example, recombination between a pair of
lysogenic E, coli strains, both Fr, usually turns out to be transductive
(and we have more detailed tests to verify this conclusion). If they
are nonlysozenic, hut ome or both is F*, they are probably mating.

Good luck to you,

Yours sincerely,

Joshua Lederberg
Professor of Medical Genetics

JL/ew

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