A 1085 bp region containing Tcrd enhancer Edelta was replaced with a loxP site flanked neomycin resistance gene cassette, which was subsequently removed via cre-mediated recombination. A 1 kb PvuII-BamHI genomic fragment containing Tcra enhancer Ealpha (Rr308) was replaced with a sequence containing a loxP site flanked neomycin resistance gene cassette and Tcrd enhancer Edelta (Rr299391). The neo cassette was subsequently deleted through cre-mediated recombination. Further cre-mediated recombination between the single loxP sites left in place of Edelta and upstream of the Edelta replacing Ealpha results in the deletion of Trdc, Trdv5, the entire Traj cluster and Trac. (J:82395)