Chilton- p. 2 
of...DNA from different species that are not known to exchange 
chromosomal DNA by natural physiological processes." This 
ambiguity in the definition of novel recombinant DNA could be 
clarified by deleting the word chromosomal from the foregoing 
statement. Alternatively, it should be stated clearly whether 
either criterion suffices, or whether both must be fulfilled, 
2. It is stated that the Director of NIH... shall prepare 
the list of those combinations of DNAs... which are not considered 
novel for this purpose and are therefore not covered by these 
Guidelines. Will any other criteria be employed in deciding 
which combinations are placed on the list? If so, the criteria 
which may be invoked should be mentioned here for clarity. For 
example would the pathogenicity of the organism used as host 
be of additional concern? Would the conjugative promiscuity 
of the plasmid used as vector be considered? (For example, 
would RP4, a highly promiscuous conjugative plasmid, be listed 
as a safe cloning vehicle for any of the wide range of bacteria 
into which it can be transmitted by conjugation?) 
In my opinion, some of the recombinant DNAs which would 
fulfil the criteria for exclusion stated explicitly here should 
nevertheless remain under the guidelines. As a specific example, 
the cloning of Agrobacterium Ti plasmid in E. coli should, despite 
the definition, be considered novel recombinant DNA for the present 
until the properties of such recombinant DNA have been assessed 
[Appendix A — 151] 
