32 
conditions for this category (P2 + EK1 ) can be used for plasmid and 
0 
phage, or for purified and characterized segments of plasmid and 
phage DNAs, when the risk that the recombinant DNAs will increase 
the pathogenicity or ecological potential of the host is judged to 
be minimal . 
NOTE : Where applicable, cDNAs (i.e., complementary DNAs) synthesized 
in vitro from cellular or viral RNAs are included within each of the 
above classifications. For example, cDNAs formed from cellular RNAs 
that are not purified and characterized are included under <a>, shotgun 
experiments; cDNAs formed from purified and characterized RNAs are 
included under <b>; cDNAs formed from viral RNAs are included under <c>; 
etc. 
3. Experiments with other prokaryotic host-vectors 
Other prokaryotic host-vector systems are at the speculative, 
planning, or developmental stage, and consequently do not warrant 
detailed treatment here at this time. However, the containment 
criteria for different types of DNA recombinants formed with E_. 
col i K-12 host-vectors can, with the aid of some general principles 
given here, serve as a guide for containment conditions with other 
host-vectors when appropriate adjustment is made for their different 
habitats and characteristics. 
8 
The DNA preparation is defined as purified if the desired DNA represents 
at least 99% (w/w) of the total DNA in the preparation, provided that it 
was achieved or verified by more than one procedure. 
[ 103 ] 
