d6 
Criteria for Selection of Safeguards. The selection of containment 
(safeguard) levels is dependent on the assessed possible dangers of 
the experiment. The Guidelines provide standards for evaluating the 
conceivable dangers of particular experiments involving recombinant 
DNA molecules. In the absence of evidence of any hazard actually 
occurring, these standards are based on relevant current knowledge. 
The criteria for assessing the possibility for danger are: 
(1 ) the degree to which the DNA segment has been purified away from 
other genes and shown to be free of harmful characteristics, 
(2) the biohazard associated with the DNA of the cell or microorganism 
that serves as the DNA source (e.g., genes for toxin production), 
(3) the biohazard associated with the vector that serves to transmit 
the source DNA to a recipient host cell, 
(4) the ability of the vector to survive in natural environments or 
habitats, 
(5) the kinds and number of different organisms that are susceptible 
to infection by the vector or recipient, 
(6) the biohazard of the recipient host cell that serves to replicate 
the recombinant DNA molecule, 
(7) the ability of the recipient cell to survive in natural environ- 
ments or habitats, 
(8) the ability of the recipient cell to transmit the recombinant 
DNA molecule to other cells capable of surviving in natural 
environments or habitats, 
(9) the potential of the recipient cell to obtain the source DNA by 
natural means, and 
(10) the evolutionary relatedness of the DNA source to humans. The 
potential dangers are considered to increase as the organism 
providing the source DNA approaches humans phylogenetically. 
Thus, source DNA from primate cells is considered to have 
greater potential danger than source DNA from lower eukaryotes. 
In general, the Guidelines assume that the potential hazards of organ- 
isms containing recombinant DNA are greater than those associated 
with their most hazardous components. 
