A 5-Mb YAC contig, partly supplemented with BAC contigs, was created from the distal Mhc class I region on mouse Chr 17. The gene order of Znf173-Tctex5-Mog-D17Tu42-D17Leh 89 is conserved between mouse and human but not the physical distance, supporting the independent expansion of Mhc class I genes in the so-called accordion model of Mhc evolution. The distal H2-M region includes the breakpoint of conserved synteny between mouse and human as well as the In(17)4 t-inversion. The H2-M region is rich in L1 repeats, implying that the insertion of L1 repeats may be associated with the evolutionary flexibility to break a chromosome.