Abstract: Cloning systems useful for the isolation of recombinant nucleic acid are disclosed in which the recombination of cloning-system nucleic acid and foreign nucleic acid is linked to the expression of a moiety on the surface of a host organism, the moiety being a first member of a binding pair. When recombination occurs between the nucleic acid and the foreign nucleic acid, the moiety is expressed on the surface of the host organism. The isolation of recombinant nucleic acid is then performed by attaching a second member of the binding pair to a solid support and contacting the host organism with the support. When the first member of the binding pair is expressed on the surface of the host organism, the host organism binds to the second member of the binding pair attached to the solid support, thereby selectively isolating those organisms.

Abstract: The invention relates to novel chimeric phosphoramidate oligonucleotides and their use in primer-extension methods such as DNA sequencing and nucleic acid amplification. The subject chimeric phosphoramidate oligonucleotides have both N3'-phosphoramidate linkages and phosphodiester linkages. The invention includes methods of primer extension using the subject chimeric oligonucleotides as primers. Primer extension methods of interest include nucleic acid amplification reactions, e.g. PCR, and polynucleotide sequencing reactions. In the primer extension methods of the invention, a chimeric phosphoramidate oligonucleotide primer is annealed to a polynucleotide template. After annealing, the chimeric oligonucleotide primer is extended by joining a nucleotide to the 3' end of the primer by a DNA polymerase catalyzed reaction. Other embodiments of the invention include methods of primer extension using phosphoramidate linkage containing polynucleotide templates.