13 . 
the corresponding shotgun experiment." Basically, we agree with this 
statement from the Woods Mole Guidelines. But, we do feel that a better 
definition for and test of 'purity' must be assigned. Simple one- 
dimensional electrophoresis is likely to contain contaminating DMA molecules 
to the 1 % level. Instead we would suggest two-dimensional gel electrophoresis 
is followed by cloning followed by repurification of the cloned material to 
test for original properties as a better test. In any case where purified 
but hazardous or obviously potentially hazardous DMAs are involved we would 
specify P4 containment plus strong justification and written approval by the 
recombinant DMA committee. We also maintain, that due to the 'unknowns' 
inherent in this work, all other such studies should for the forsecable 
future be kept at the P3 level containment. 
( c ) PI. A SM I P S, BACTERIOPHAGES, & OTHER VIRUSES 
( i ) Animal V i ru s_e s 
We very strongly feel that the experiments mentioned in this sectic 
of the Woods Hole Guidelines, those specifically dealing with animal 
virus DMA recombinants propogated in E. col i hosts, should be deferred 
until all of the following objections or questions are fully answered: 
1. the selection, testing, and acceptance of real standards of 
'purity' for the DMAs in question; 
2. some real criterion for certain judgement that DMA's go not 
contain 'harmful' genes 
3. that genome segments are absolutely free of latent or active 
genes involved in cellular transformation and oncogenesis; the 
division of tumor virus genomes into oncogenic and ncn-oncoce-nic 
sections, although reasonably convincing as it stands, is none- 
theless an operational definition arising out of specific, 
limited experiments. Until the function in mammalian cells of 
• all gene products from "non-oncogenic portions" of oncogenic 
viruses is known, putting them in E. c ol i should be deferred. 
4. the epidemiological capacity and comoetence is shown to exist 
for the surveillance and discovery of any possible 'accident' 
with oncogenic or pathogenic viruses. 
( i i ) PL ANT VI R USES 
From the above sections of this critique, our skepticism as to 
the existence of any proof or definition of DMA 'purity' should be as 
obvious as our strong ojections to the use of an airborne and widely 
distributed host such as _E. co l i . We consider segments of a virus to be 
as potentially hazardous as the complete genome. It would therefore be 
prudent to propose P3 containment for all plant virus experiments with 
P4 being mandatory in the case of oncogenic plant associated plasmids or 
viruses. 
(iii) ^Km.qjJ_C_PLAj;jlID_D.MA 1 
We feel that such experiments with DMA from warm-blooded 
eukaryotes should be deferred indefinitely for the reasons outlined for 
shotgun experiments on eukaryotic DMA recombinant, molecules. For similar 
reasons we feel t.hut plasmid DMAs from all other eukaryotes should be 
limited to P4 containment until safer host-vector systems are developed 
and documented. 
[ 364 ] 
