STANFORD UNIVERSITY MEDICAL CENTER 
STANFORD, CALIFORNIA 94305 
DEPARTMENT OF BIOCHEMISTRY 
PAUL BERG 
Jack, Lulu and Sam Willson 
Professor of Biochemistry 
December 5, 1977 
Dr. Donald S. Fredrickson 
Director 
National Institutes of Health 
Building 1, Rcom 124 
Bethesda, MD 20014 
Dear Don, 
Last week Bernie Talbot asked me to try to rewrite the 
definition of recombinant DNA molecules for the revised ver- 
tion of the Guidelines, so as to include molecules containing 
synthetic DNA sequences. He also asked me to indicate my views 
on what level of containment could be recommended for experi- 
ments with such synthetic DNA segments. 
Enclosed is what I came up with. Seems simple enough but 
perhaps I have overlooked something. Nevertheless, it should 
be useful as it is or in any amended form. 
Good luck in your efforts for this round of revisions. 
With best regards. 
Sincerely yours, 
PB : ab 
c.c. B. Talbot 
[Appendix A — 83] 
