High frequency de novo alterations in the long range genomic structure of the mouse pseudoautosomal region

The pseudoautosomal region (PAR) is a segment of shared homology between the X and Y chromosomes. Here we report physical linkage of three mouse PAR probes: DXYHgu1, DXYMov15 and (TTAGGG)(n). Steroid sulphatase (Sts) maps distal to these three probes, indicating that there is an internal array of the telomere sequence (TTAGGG)(n) in the PAR. Pseudoautosomal Pad restriction fragments, up to 2 Mb in size, are unstable in C57BL/6 x C57BL/6 crosses. New alleles, often several hundred kilobases different in size, occur at a sex-averaged rate of similar to 30% per allele. Such frequent large-scale germ-line genome rearrangements are without precedent in mammals.