A high-resolution radiation hybrid map of sheep chromosome X and comparison with human and cattle.

A radiation hybrid (RH) map of sheep X chromosome (Ovisaries; OARX) containing 146 physically anchored loci was generated in this study, providing information for comparative X chromosome analysis between the maps of sheep, human, and cattle. Primers typed on the USUoRH5000 ovine whole-genome radiation hybrid panel were designed from sequences predicted to be on the ovine X chromosome, based on comparative mapping within the virtual sheep genome browser (v1.2). The resulting RH map for the ovine X chromosome consists of 4 linkage groups composed of 76 BAC end sequences (BES), 28 gene loci that were confirmed within ovine BAC clones in the CHORI-243 ovine BAC library, 28 additional gene loci from the ovine comparative map and 14 polymorphic sequence tagged sites (STS) from the OARX linkage map. This first-generation RH map of OARX contributes to the expansion of a comprehensive ovine genome map for sheep and provides evidence of rearrangements in loci order compared to the human and cattle orders.