7 
would be required for SV 40 to acquire Uio capacity to produce 
cancer in hiuiiann? Perhaps this could occur by the acquisition 
of a piece of DNA not normally considered "harmful" rn the 
donor organism, but spcocifying control signals coixmion to many 
organisms. VJe have the example of influc:nza virus, which 
undergoes a natural reassortment of its RI\’A containing 
1 / 
subunits so as to produce strains which can cause effects 
ranging from a case of the sniffles to a world-wide epidemic. 
The genetic determ.inants of why influenza virus covers such a 
wide spectrum of virulence are unknown. Thus v;e really have 
absolutely no information to enable us to predict the effect 
upon th,e infectivity, virulence or host specificity of adding 
any DNA to a viral genome. 
(5) A similar argument can be extended to bacteria. The 
assumption is made in the Guidelines that the addition of almost 
any functional piece of "foreign" DNA v;ill adversely affect its 
capacity to survive in its normal host. The extent to which that 
assumption is or is not valid is not known, with so little data 
to go on. Again, any gene in the context of a new organism must 
be considered to possess the potential for being "harmful," since 
the production of toxic or ha3;mful gene products are by no means 
the only ways in which recorabinant DNA containing bacteria could 
exert pathologic effects. 
1/ B. D. Davis, ct al . , Mic rob iolog y , 131B (2nd Ed., 1973). 
Appendix K — 61 
