1 
, I. 
FOREWORD 
Recent developments in molecular genetics, particularly in the 
last 4 years, open avenues to science that were previously inaccessible. 
In the ''recombinant DNA" experiments considered here, genes-- 
deoxyribonucleic acid (DNA) molecules --from virtually any living 
organism can be transferred to single cells from certain completely 
unrelated organisms. These experiments depend on the ability to join 
together genetic material from two different sources and then to propagate 
the resulting hybrid elements in single bacterial and animal cells. 
For example, genes have been transferred from bacteria of one 
species to bacteria of another. And genes from amphibians or insects 
have been introduced into the bacterium Escherichia coli . If the 
recipient cell is then allowed to multiply in the laboratory, it will 
propagate these newly acquired genes as part of its own genetic com- 
plement. 
It should be understood that genetic recombination itself (other 
than what is referred to as "recombinant DNA") is a well-known phenom- 
enon and has been occurring in nature for millions of years. The 
recombining of genetic material (DNA) is an integral part of sexual 
reproduction. 
The new recombinant DNA technique has resulted in a profound and 
qualitative change in the field of genetics. Hypotheses and ideas that 
were not previously testable can now be rigorously investigated. Under- 
standing of basic biological phenomena has already been enhanced and will 
certainly be enlarged as experiments proceed. The promise of recom- 
binant DNA research for better understanding and improved treatment 
of human disease is also great. Further experimental data will be 
required to delimit the benefits that may be derived through these 
techniques. 
There is also a possible risk that the properties of a microorganism 
with foreign genes might be altered so that it could cause disease or 
adversely affect the environment if it should escape from the laboratory 
and infect human beings, animals, or plants. Throughout the world 
many recombinant DNA experiments have been conducted during the 
past 5 years and are continuing today. To date, no known hazardous 
organism has been produced in this work. Thus, the risk of converting 
harmless organisms to harmful ones by recombinant DNA experiments 
remains hypothetical, but cannot be ignored. Further work will even- 
tually determine the limits of these hypothetical risks. Meanwhile, 
it is assumed that hazards of varying degrees may exist and that some 
precautions are justified to minimize the probability of their occurrence. 
