A region flanking H-2K is duplicated to a distant site in most mouse t haplotypes

Mouse t haplotypes contain at least one inversion, which encompasses the major histocompatibility complex, relative to their wild-type counterparts. A DNA probe for a single copy sequence which flanks the H-2K region in inbred strains was found to have undergone further rearrangements in the t haplotypes. In most t haplotypes, this sequence is duplicated at a distant site, and the two regions show 1 % recombination. The length of homology shared by the two sites is likely to be at least 10–15 kb. Three different alleles, as defined by restriction fragment length polymorphisms, were found for each of the two sites among different t haplotypes. These may reveal evolutionary relationships among these chromosomes.