of RNA processing for the expression of eukaryotic genes 
(pp. 33057-33062) . Though risk assessment experiments were 
proposed at Falmouth, they have generally not been carried out, 
and, needless to say, the proposed revisions in containment 
levels for shotgun experiments are not based on their results. 
Many questions about the integrity of bacterial host-vector 
systems and the cloning of tumor viruses have been treated 
above. Here we discuss some of the unanswered questions about 
the expression of eukaryotic DNA sequences in bacteria. 
In footnote 12 to the "Introduction and Overview" of the 
"Decision of the Director," Dr. Martin of NIH concludes that: 
(1) cloning of chromosomal DNA in E. coli DNA will 
pose little, if any, risk since the (RNA) maturation 
mechanisms have never been observed in prokaryotes ; 
and (2) investigators who wish to develop prokaryotic 
cloning systems for the purpose of synthesizing useful 
biological products will utilize cDNA [complementary 
DNAl copies of functional mRNAs [messenger RNAs ] or 
synthetic DNA with a nucleotide sequence derived from 
a known amino acid sequence as DNA inserts, (p. 33047). 
However, § III-A-1 does not require that cDNA made from 
uncharacterized and unpurified eukaryotic message be cloned 
at a higher level of containment than the DNA from the same 
cells. Shotgun cloning of cDNA circumvents the barrier to 
functional expression presented by split genes and should be 
carried out at current levels of containment. Multicellular 
organisms which undergo development generally produce hormones 
which are powerful toxins if present at the wrong time in the 
organisms' life cycle. The possible inadvertent cloning of 
[A-197] 
