Novel sequences conserved on the human and mouse X chromosomes.

We have cloned and mapped 28 single-copy probes from a pool of cosmids derived from the human X chromosome. Four of the probes detected strongly conserved sequences in murine DNA; all have been localized to the proximal region of the human X chromosome short arm. Comparative mapping of these sequences in the mouse genome demonstrates that, while X linkage is conserved, this region of the human X chromosome is not maintained as a contiguous segment on the mouse X chromosome. The mapping of one novel conserved sequence between Plp and Pdha1 on the mouse X chromosome defines a previously unknown region of homology. The mapping of another probe that detects a novel sequence family (DXF34) close to the X chromosome centromere in both species suggests that a block of pericentromeric material is conserved between the X chromosomes of man and mouse.