JUN 1 8 1962
YALE UNIVERSITY

DEPARTMENT OF MICROBIOLOGY 310 CEDAR STREET
NEW HAVEN 11, CONNECTICUT

June 15, 1962

Dr. Joshua Lederberg

Department of Genetics

Stanford University Medical School
Palo Alto, California

Dear Josh:

Thanks for the note. Herewith my analysis of the present
semantic confusion:

State of bacterial Lederberg Clark & Adelberg
genetic element designation designationt
(1) Only on chromosome chromogene chromosomal gene

(2) Alternating between a
chromosomal location and episome episome a
an extra-chromosomal location eo,

N
y
*

(3) Extra-chromosomal only (TERM NEEDED) plasmid
(4) Capable of extra-chromosoma} re
state (whether or not capable plasmid (TERM NEEDED)

of chromosomal attachment)

(+ Our interpretation of your 1952 proposal is the same as Jacob & Wollman's <=
see pages 327-328 of their book).

The problem is that we need four terms to cover what may be
operationally known about any given element. Your usage leaves us without
a term for obligatory extra-chromosomal elements (which may well be an
important concept); our usage leaves us without a term for elements which
we find in the extra-chromosomal state but for which an alternate chromosomal
state is undetermined.

Thanks for the word on the F- state of what I presume were equi-
valent to "het" diploids.

Greetings to Esther.
AS ever,

oA

Edward A. Adelberg

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