Figure 10.

Changes in the pseudoautosomal boundary mapped onto the Mus phylogeny. Ancestral pseudoautosomal region (PAR), including unassembled repetitive regions, represented in gray. X-unique sequence translocated to the Y, expanding the PAR, shown as colored blocks. There are now at least three independent alterations of the boundary and/or organization of the PAR (inverted triangles): one in the ancestor of M. musculus (after the divergence from the M. spretus–M. spicilegus clade), expanding the PAR to include exons 4–8 of Mid1; the previously documented expansion in CAST/EiJ; and the rearrangement we describe in PWK/PhJ. Approximate divergence times are shown below the tree, and schematics of the organization of each allele at right.