Schematic drawing showing the selection cartridge of the plasmid pGBG1 after the insertion of IS 711. Brucella strains containing these plasmids were resistant to tetracycline. The IS711 insertion is represented by a white box flanked by grey arrowheads. The target sequence is indicated and the duplicated bases appear as underlined capital letters. The primers used to amplify and determine the precise location of insertions in the selection cartridge are indicated with the primer name and black arrow heads.