Diagram of the targeting strategy to generate the Rx-tTA: TetOp-Cre knock-in allele.

<p>A. The targeting vector consists of homology arms to exon 2, intron2/3, exon 3, 3′ UTR and 3′ genomic sequence. Sequence containing the tTa/Cre cassette and the neomycin resistance gene was inserted within the 3′UTR. The final targeted locus following the action of flp recombinase is also depicted. The black arrowheads indicate FRT sites and the red numbers denote the location of primers used for genotyping. B. PCR was performed with the indicated primers on genomic DNA from Rx-tTA: TetOp-Cre mice crossed with the flp recombinase line. IRES: internal ribosomal entry site, tTA: tetracycline transactivator coding sequence, TetO: operator of the <i>E. coli</i> tetracycline resistance gene, Neo: neomycin resistance gene, Cre: Cre-recombinase coding sequence, pA: poly-adenylation sequence, TK: Thymidine kinase.