Reverse or bidirectional Zoo-FISH suggests that synteny between porcine chromosome 12 (SSC12) and human chromosome 17 (HSA17) is completely conserved. The construction of a high-resolution radiation hybrid (RH) map for SSC12 provides a unique opportunity to determine whether chromosomal synteny is reflected at the molecular level by comparative gene mapping of SSC12 and HSA17. We report an initial, high-resolution RH map of SSC12 on the 12,000-rad IMNpRH2 panel using CarthaGene software. This map contains a total of 320 markers, including 20 microsatellites and 300 ESTs/genes, covering ∼4836.9 cR 12,000. The markers were ordered in 16 linkage groups at LOD 6.0 using framework markers previously mapped on the IMpRH7000-rad SSC12 and porcine genetic maps. Ten linkage groups ordered more than 10 markers, with the largest containing 101 STSs. The resolution of the current RH map is ∼15.3 kb/cR on SSC12, a significant improvement over the second-generation EST SSC12 RH7000-rad map of 103 ESTs and 15 framework markers covering ∼2287.2 cR7000. Compared to HSA17, six distinct segments were identified, revealing macro-rearrangements within the apparently complete synteny between SSC12 and HSA17. Further analysis of the order of 245 genes (ESTs) on HSA17 and SSC12 also revealed several micro-rearrangements within a synteny segment. A high-resolution SSC12 RH12,000-rad map will be useful in fine-mapping QTL and as a scaffold for sequencing this chromosome.
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