THE UNIVERSITY OF NORTH CAROLINA 
AT 
CHAPEL HILL 
Division of Health Affairs 
The School of Medicine 
Department of Bacteriology and Immunology 
The University of North Carolina at Chapel Hill 
804 Faculty Laboratory Office Building 231 H 
Chapel Hill, N.C. 27514 
29 August 1979 
Director 
Office of Recombinant DNA Activities 
Building 31, Room 4-A52 
National Institutes of Health 
Bethesda, Maryland 20205 
Dear Sir: 
I am writing to state my support in favor of ammending the 
Guidelines for Research Involving Recombinant DNA Molecules 
(43FR60108) concerning certain Eh coli K-12 Host-Vector systems. 
Because of increased knowledge of the safety of the system, I 
favor exempting from the Guidelines research carried out with 
recombinant DNA molecules propogated in Eh coli K-12 not containing 
conjugation-proficient plasmids or generalized transducing phages 
when lambda or lambdoid phages or non-conjugative plasmids are used 
as vectors. This certainly makes sense when plant genome DNA is 
being cloned using such a system. 
Robert Twarog C, P ]XT) 
Associate Professor 
RT/jb 
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