APPENDIX E 
are lower if the DNA is isolated from embryonic tissue, or germ I i ne mater i a I , 
since such material is less likely to be contaminated by pathogenic viruses 
or other adventitious agents than is adult tissue. Thus, if the foreign DNA 
is from cold-blooded vertebrates, P2 and EK2 are required but P2 and EK1 can 
be used if the DNA is from embryonic or germ I ine tissues. If the cold 
blooded vertebrate is known to produce a potent toxin, P3 and EK2 must be 
used. In some instances, lower eukaryotes for example, the guidelines require 
more or less stringent conditions depending on whether or not the source of 
foreign DNA is known to be pathogenic or toxigenic, or might be infected 
with a pathogen, or is known to make a harmful product. 
Table I I summarizes the guidel ines for shotgun experiments when the source 
of the DNA is a prokaryotic organism. First, those prokaryotes which are known 
to exchange genetic information with E. col i in nature are considered. The 
containment requirements are low for this group and vary with the pathogenicity 
of the source of foreign DNA. When the source of foreign DNA is a prokaryote 
that does not naturally exchange genetic material with E. co I i , the contain- 
ment recommendations are high. It is assumed that the more similar the DNAs 
of donor and host, the greater the probability of expression of foreign DNA, 
or of possible derepression of host genes. In those cases where the donor 
exchanges DNA with E. co I i in nature, it is unlikely that recombination 
experiments will create new genetic combinations. When prokaryote donors 
hot known to exchange DNA with E. col i in nature are used, however, there 
is a greater potential for new genetic combinations to be formed and expressed. 
Character i zed clones obtained from shotgun experiments may not be as 
potentially hazardous as the original mixture of cells. Cloning of the 
Appendix E — 15 
