APPENDIX E 
involving such mixtures of DNA fragments are assumed to be of relatively 
high potential hazard because of the greater likelihood of dangerous and 
unknown genes being introduced into a recipient cell compared to experiments 
with a single, highly purified fragment. Purified fragments containing 
mainly genes whose properties are known and are not harmful, offer less 
potential hazard than a shotgun experiment. In some instances the foreign 
DNA will itself be derived from extrachromosoma I genetic elements. Such 
extrachromosoma I elements include the DNA of animal viruses, plant viruses, 
other eukaryote organelles such as mitochondria and ch I orop I asts , as well as 
prokaryote plasmids or bacteriophages, of the same type used as vectors. 
Each of these cases is treated separately in the guidelines. The prokaryote 
sources are treated differently, depending on whether the source of the 
"foreign" DNA is an organism that does or does not exchange genetic information 
with E. CO I i in nature. 
Guidelines for experiments with E. col i host-vector systems . Table 1 
shows the containment required for shotgun experiments when the foreign DNA 
is a mixture of fragments derived from eukaryotes. The physical and biological 
containment is listed for various possible DNA sources: both must be used as 
they complement each other. For example, DNA from primates requires the most 
stringent containment, since the estimated potential hazard either from genes 
that might function in humans with untoward effects, or from pathogenic viral 
DNAs residing in primate tissue is judged to be most serious. The experiments 
require either P3 and EK3, or P4 and EK2, and it should be recalled that only 
the latter combination, P4 and EK2, is feasible at present and even then only 
at the limited number of P4 facilities. Another point of interest is that in 
two instances, primates and cold blooded vertebrates, containment requirements 
Appendix E — 14 
