Biochemical method for inserting new genetic information into DNA of simian virus 40: Circular SV40 DNA molecules containing Lambda phage genes and the galactose operon of Escherichia coli.

First recombinant DNA molecules generated. Digital facsimile from PubMedCentral at this link.

In 1980 Berg was awarded half of the Nobel Prize in Chemistry "for his fundamental studies of the biochemistry of nucleic acids, with particular regard to recombinant-DNA." The other half was awarded  to Walter Gilbert and Frederick Sanger "for their contributions concerning the determination of base sequences in nucleic acids."