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the supercautious mood prevalent at that time rather than a 
clear-cut scientific judgement. In my view requiring that a 
DNA fragment should be 90-95% pure (as judged by at least two 
different analytical procedures) to remove it from the "shotgun" 
classification is more realistic and no less safe. Requiring 
that a DNA fragment be >99% pure prior to cloning asks for the 
most stringent and detailed documentation without any real 
advantage. For example, if prokaryote or mouse DNA, can be 
"shotgunned" into polyoma vectors under P2 conditions, I do 
not understand why segments of DNA from eukaryotes e.g. or 
gamisms that do not produce potent polypeptide toxins as 
exemplified by yeast. Drosophila or even rabbit, need be >99% 
pure prior to cloning in polyoma! What is the concern if they 
were 50, 90 or 95% pure? 
In the paragraphs of Section III-A-2, dealing with 
cloning various virus DNA and cDNA sequences, the word 
purified appears throughout without referencing to footnote 
38 ar 40. Does purified in each of these cases mean >99%? 
If so, is that intentional or inadvertent? In my view if a 
particular segment was 90-95% pure that would be sufficient 
since the isolation and screening of only 20 to 50 clones 
would insure the recovery of the desired recombinant with 
little or no increased risk. Even with DNA segments that are 
50% pure half the clones would be the desired ones. In short 
by recommending that segments be greater than 90% pure only a 
small number of clones need to be isolated and examined, 
thereby, drastically reducing the probability of creating or 
releasing unexpected recombinants to a vanishingly small number. 
5. I am particularly unhappy about the recommendations 
PRG-NIH proposes regarding the development, review and 
certification of new HV systems. The breakthrough with yeast 
transformation and the ability to propagate exogenous DNAs in 
S . cerevesiae has very important ramifications in extending the 
recombinant DNA technique for basic and applied purposes. Yet 
ORDA and RAC are confounding and, I believe obstructing these 
developments. Long delays in coming to a conclusion are 
particularly frustrating. I suggest that as such scientific 
problems arise ad hoc committees, composed of knowledgeable and 
responsible scientists in the relevant disciplines, should be 
convened as quickly as possible to examine the issues and 
advise RAC on possible courses of action. The U.S.-EMBO 
workshop and report is a model of how this can be done. In 
this way actions on several important issues could be proceeding 
in parallel rather in series. Such committees or workshops 
should already be at work trying to assess the possible risks, 
if any, of cloning foreign DNAs in yeast and in B. subtilus . 
As it now stands no decision is tantamount to a ban on these 
experiments. Can we really defend or condone banning the 
introduction of Drosophila or mammalian DNAs into S. cervesiae? 
Even with the uncertainties that existed at Asilomar cloning 
such DNAs in E. coli K12 was not forbidden. While the inquiries 
are proceeding there should be recommendations of interim 
physical containment and specified biological properties to permit 
such experiments to proceed. Investigators would be informed 
[A-211] 
