Breakpoint mapping positions the callipyge gene within a 450-kilobase chromosome segment containing the DLK1 and GTL2 genes.

Abstract

We have previously mapped the ovine callipyge (CLPG) gene,causing a muscular hypertrophy with parent-of-origin-dependentexpression referred to as polar overdominance, to a 4.6-cM chro-mosome interval on distal OAR18q flanked by microsatellitesIDVGA30 and OY3 (Cockett et al. 1996; Shay et al. 2000). BACcontigs spanning this interval were constructed by using bovine(Shay et al. 2000) and subsequently ovine (Segers et al. 2000)reagents. We herein report the isolation of eight novel microsat-ellite markers from these contigs, yielding a marker density of onemicrosatellite per 68 kilobases and the use of these novel markersto position the CLPG gene by breakpoint analysis within a ≈450-kilobase chromosome segment.Five BAC clones jointly spanning most of the IDVGA30–OY3interval were selected from the ovine BAC contig (BACs: 724D11,239G7, 218E10, 497C1, 265F11). BAC DNA was digested tocompletion with three four-cutters yielding blunt-ended restrictionfragments (AluI, HaeIII, and RsaI) used either separately or com-bined. Restriction fragments containing microsatellites were de-tected by standard Southern blotting and hybridization with a(CA)