Patent ID: 7846718

Claim:
A vector comprising the following operably linked DNA fragments: an origin of replication (1) allowing replication in a recipient cell; a selectable marker region (2) capable of being expressed in said recipient cell; and a chimeric DNA construct comprising in sequence: a promoter or promoter region (3) capable of being recognized by a prokaryotic RNA polymerase; a first recombination site (4), a second recombination site (5), a third recombination site (6) and a fourth recombination site (7); a 3′ transcription terminating region (8) functional in said recipient cell; wherein said first recombination site (4) and said fourth recombination site (7) are capable of reacting with a same recombination site, and said second recombination site (5 ) and said third recombination site (6), are capable of reacting with a same recombination site; and wherein said first recombination site (4) and said second recombination site (5) do not recombine with each other or with a same recombination site; or said third recombination site (6 ) and said fourth recombination site (7) do not recombine with each other or with a same recombination site.