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permissive cells are infected with mutant genomes which 
can not complete the infectious cycle. I foresee the 
development of eukaryote plasmids constructed from 
portions of Polyoma or SV40 DNA that can propagate in 
permissive mammalian cells without killing the cells or 
producing progeny virus. That contingency is obscured 
by using the words non-permissive cells in connection 
with non-productive infections. 
b) I am totally confused by the wording or intent of 
paragraphs III-C-1-a- (1) - (b and c) dealing with polyoma 
vectors particularly when they are compared with the 
analagous instructions for the SV40 DNA vectors in 
paragraph III-C-1-b- (1) - (b) . The word defective and 
intact are not appropriate. How can one use an intact 
polyomaDNA as a vector? If an exogenous DNA sequent is 
introduced into the polyoma DNA it is no longer intact; 
moreover, the introduction of foreign DNA into the 
polyoma DNA will render it defective because it will 
inactivate an essential function or enlarge the DNA to 
a size that prevents its encapsidation-hence it becomes 
defective as a potential virus. I think The Guidelines 
want to distinguish between the cases where a recombinant 
is defective, therefore requiring a helper, and the very 
rare case where a recombinant is non-defective and 
does not need a helper for multiplication. The 
operational definitions that define the containment 
requirements should be whether the propagation of the 
recombinant is helper-dependent or independent. 
c) In assigning P2 containment to experiments in which 
african green monkey cell DNA is propagated with SV40 DNA 
vectors, were human and rhesus monkey cell DNA to be 
excluded from this category? Human and some other 
primate cells do support SV40 multiplication and, 
therefore, presumably cell-virus DNA recombination 
does occur naturally; shouldn't paragraph III-C-1-b- (a) - 
(2) read "uninfected primate cells in which SV40 is 
known to multiply"? I am also puzzled by the logic which 
permits P2 containment for propagating monkey DNA in 
SV40 vectors but retains a P3 containment requirement 
for propagating recombinants with yeast. Drosophila or 
rabbit DNA (compare paragrahs III-C-1-b- ( 1) - (a) - (2) and 
III-C-1-b- (1) - (b) . 
4. Another point which needs further consideration is 
the continued use and definition of the words "purified" 
and "vigorously characterized" (see paragraph III-A) . In as 
much as I drafted the wording to explain the terms appearing 
in footnote 38 and 40 of Section V at the RAC meeting in 
La Jolla in December 1975, I know that its adoption reflected 
[A-210] 
