B2RT is the target site for the B2R recombinase. It is composed of two 17bp inverted repeats flanking a 5bp spacer sequence: 5'-GAGTTTCATTAAGGAATaactaATTCCCTAATGAAACTC-3'. B2R mediates recombination between a pair of B2RT sites. This recombination event results in genetic modification, the nature of which is influenced by the relative orientation (direct or inverted), location and composition of the two recognition sites (FBrf0214794).