45 
In addition, the Guidelines prohibit other experiments that may or 
may not prove to be risky but for which the nature of the possible 
hazard can be described and is demonstrably undesirable, such as the 
formation of recombinant DNAs containing the genes for production of 
dangerous toxins (see 2 below). Finally, because the escape of 
substantial numbers of organisms is inherently more likely to yield 
untoward effects than an accidental release of a small number, should 
conjectural hazards prove real, the Guidelines prohibit release into 
the environment of any organisms containing a recombinant DNA 
molecule (see 4 below) or the carrying out of experiments involving 
large volumes of recombinant DNA organisms containing harmful 
material (see 6 below). The following is a more detailed description 
of the experiments that are prohibited (Section III-A of the Guidelines): 
(1) Any experiment in which any portion of the DNA is derived 
from an organism that is itself a biohazard of greater than 
low risk as determined by conventional methods of risk-assess- 
ment. For this purpose, low-risk organisms correspond to 
those listed as class 1 or 2 agents by the Center for Disease 
Control, or as low-risk oncogenic viruses by the National 
Cancer Institute. The Guidelines further state that the 
prohibition extends to the use of DNA from any cells known 
to be infected by agents of greater than low risk. 
(2) The deliberate formation of recombinant DNAs containing 
genes for the biosynthesis of potent toxins. This prohibition y 
precludes the use of DNA from organisms known to produce 
potent toxins, such as certain bacteria (for example, those 
producing botulism or diphtheria toxin) and certain insects, ! 
amphibians, and snakes (those known to produce potent 
venoms) unless purified DNA known to be free of the genes 
for the toxins and venoms is used. 
(3) The deliberate creation of recombinant DNAs involving the 
DNA of plant pathogens, if the recombinants are likely to 
increase the virulence and host range of the pathogen. 
V 
(4) The deliberate release into the environment of any organism 
containing a recombinant DNA molecule. 
(5) The transfer, by recombinant DNA techniques, of genes for 
drug -resistance traits to microorganisms that are not known 
to acquire those genes naturally, if such acquisition could 
compromise the use of the drug to control disease agents in 
human or veterinary medicine or agriculture. It should be 
recognized that a large number of microorganisms do acquire 
such traits in nature, by intra- and interspecies recombination. 
Therefore, experiments involving, for example, the transfer 
of a large number of drug resistance traits into E. coli are 
not prohibited, since E. coli is known to acquire - such traits 
in nature. 
