Several genes involved in human genetic diseases map to the Xq22 band on the long arm of the human X chromosome. We have constructed a long-range restriction map of the most proximal part of Xq22. Initially, pulsed-field gel electrophoresis, in combination with rare-cutting restriction enzymes, was used to try and establish physical linkage of 11 polymorphic and non-polymorphic DNA markers. This approach resulted in the construction of three long-range restriction maps around groups of physically linked Xq22 markers that spanned over 5.0 Mb of DNA. Yeast artificial chromosome clones were used to organize the three long-range maps onto a contiguous 5.2-Mb stretch of Xq22. The order of markers in this region was shown to be cen-GLA-DXS178-DXS101-DXS83-DXS24-DXS101-DXS54-PLP-DXS94-DXS147-DXS17-DX S87-tel. The results of this study suggest that the proximal part of Xq22 may be rich in genes. Construction of a physical map for this region will, therefore, facilitate the localization and subsequent isolation of novel genes.
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