27 
The ability of a plasmid to be transferred from the original 
laboratory host to another cell and thereby perpetuate itself is also 
important. (See Guidelines, Section III-B-1 . ) In short, certain plasmids 
are incapable of being transferred except under particular and infrequent 
conditions. Others transfer more readily. Again, no generalization 
concerning the effect of a foreign DNA fragment on transferability can 
be made. Since the ability to be transferred depends on multiple 
factors (11), it is not likely to be increased by insertion of a single 
foreign DNA fragment. 
Analogous issues as they relate to viral vectors are discussed 
in some detail in the Guidelines (Section III-B-1 for bacterial viruses 
and Section III-B-4-a for animal viruses: see also reference 11 of 
this section. ) Two recent papers give evidence that bacteriophage 
lambda vectors with inserted DNA are less viable than such vectors 
without inserted DNA 0 2, 13). 
b. The effect of bacteria and viruses containing recombined 
DNA on other forms of life 
The analysis leading to the Guidelines centered on the possibility 
of deleterious effects, since the concern was the health and safety 
of living organisms, including humans, and the environment. Agents 
constructed by recombinant DNA technology could prove hazardous 
to other forms of life by becoming pathogenic (disease -producing) 
or toxigenic (toxin-producing), or by becoming more pathogenic or 
toxigenic than the original agent. v 
There are two basic mechanisms by which a recipient micro- 
organism might be altered with regard to its pathogenicity or toxicity 
as a result of a resident recombinant: 
(1) The recombinant DNA may result in formation of 
a protein that has undesirable effecTs 
The case in which bacterial cells are used as carriers of foreign 
DNA is discussed first. A foreign protein, specified by the foreign 
DNA, might act after being liberated from the microorganism, or 
it could function within the microorganism and alter, secondarily, 
normal microbial cell function in such a way that the cell is rendered 
harmful to other living things. Either means depends on the expression 
of the foreign genes; that is, the information in the foreign genes 
must be used by the recipient bacterium to produce a foreign protein. 
Examples of proteins that might prove harmful to other organisms are 
hormones, enzymes, and toxins. 
