ROCHE INSTITUTE OF MOLECULAR BIOLOGY 
Nutley, New Jersey 07110 
August 14, 1979 
Dr. Donald S. Fredrickson 
Di rector 
National Institutes of Health 
Bethesda, Maryland 20205 
Dear Dr. Fredrickson: 
I am writing in response to your request for comments 
on the proposal (of Drs. W. Rowe and A. Campbell) that 
recombinant DNA experiments involving Z. coli K-12 hosts and 
non-conjugative plasmids or bacteriophage X vectors be 
exempt from the NIH Guidelines. I would like to express 
support for this proposal which seems most sensible in view 
of the bulk of scientific data now at hand. We believe 
that, as more scientific information becomes available in 
this area, the Guidelines should be changed accordingly. 
Sincerely yours, 
Herbert Weissbach, Ph.D. 
Roche Recombinant DNA 
Biosafety Committee Chairman 
HW/kj 
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