Cloning of BAC inserts into the BGM vector. (A) Genomic structures of mouse chromosome 7 and the BAC inserts used in this study. The BAC clones cover a portion of the class I OR locus on chromosome 7, share 82 kb overlapping region and are oriented in opposite directions in the BAC vector. A large triangle depicts MOR42-3, black triangles indicate other OR genes, and the gray triangle represents the pseudo-OR gene . (B, C) The cloning of BAC1 and BAC2 into the BGM vector was confirmed by I-PpoI/CHEF (left panels in B and C) and Southern blotting (right panels in B and C). The representative BGM vectors with transferred BAC1 and BAC2 inserts were digested with I-PpoI and resolved by CHEF. The open arrowheads indicate BAC insert bands, and the closed arrowheads indicate the BGM vector. Purified original BAC clones and genomic DNA from representative BGM clones were digested with EcoRI or HindIII and hybridized with the original BAC clones as probes. The BGM recombinants showed a band pattern identical to the original BAC clones (lane: BAC), except for the bands corresponding to the BAC end sequences from EcoRI-digested BAC1; the closed arrowhead indicates a BAC-specific signal, and the open arrowheads indicate BGM-specific signals from EcoRI-digested BAC1. In other digestion patterns, the bands of the BAC end sequences were overlapping and indistinguishable from insert signals predicted from restriction maps of BAC clones and the BGM vector. Numbers above lanes are the BGM clone numbers. In lane M, lambda/HindIII fragments or a lambda DNA concatemer was used as a size marker.