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 loxP site flanked neomycin resistance gene cassette. 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 in place of Ealpha results in the deletion of Trdc, Trdv5, the entire Traj cluster and Trac. (J:82395)