Mapping of DNA markers close to the fraglle site on the human X chromosome at Xq25–3

Abstract
We report the identification of a new RFLP detected by the DNA probe MN12, which is linked to both the fragile site on the X chromosome at Xq27-3 and the highly polymorphic locus detected by Stl4 (DXS52). In situ mapping confirms the localisation of MN12 distal to the fragile site. A detailed physical analysis of this region of the X chromosome using pulsed-field gel electrophoresis has shown that MN12, Stl4 and DX13 (DXS15) are physically linked within a region of tyyOkb. A long range restriction map around the MN12 locus reveals at least two candidate HTF islands, suggesting the existence of expressed sequences in this region.