3 
there was strong public support for retaining the prohibition, 
would you object if the section were to specify procedures for 
constructing and handling (a) recombinant DNA molecules and (b) 
organisms and viruses containing recombinant DNA molecules? 
Thus, in the exemption section, most recombinant DNA molecules 
outside of organisms and viruses that are not covered under 
the prohibited experiments would be exempt from the Guidelines. 
o In light of the comments on the definition, I am considering 
one that would not include the phrases "the capacity to infect" 
and "natural physiologic processes." A substitute definition 
would speak to "molecules that have been constructed outside 
living cells by joining natural or synthetic DNA segments 
to DNA molecules that can replicate or be integrated into 
the genome of a living cell." I would appreciate your views 
on this suggestion, including the addition of "synthetic 
DNA segments" to the definition. 
• In light of the comments on the criteria and procedures for 
a listing of non-novel exchangers, new language has been 
drafted for experiments to be exempted jfrora the Guidelines. 
A copy of a letter with the NIH draft on exemptions that I sent 
to Dr. Spizizen and his Working Group is enclosed for your 
reviev/. Please note that no prohibited experiments may be 
exempt. To emphasize the importance of this concept, prohibited 
experiments would be transposed from Section III to Section I 
and would appear before the exempted experiments. I would 
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