Construction and characterization of an ovine BAC contig spanning the callipyge locus

We describe the construction of an ovine BAC contig spanning a 4.6 centimor gan (cM) chromosome segment known to contain the callipyge (CLPG) locus. Th e contig comprises 21 ovine BAC clones jointly covering approximately 900 k ilobases (Kb). Two gaps in the BAC contig, spanning 10 and 7.5 Kb, respecti vely, were bridged by long range PCR. The corresponding chromosome region w as shown to be characterized by an unusually low Kb to chi ratio (164 Kb/cM ) and a high density of NotI sites (1:126 Kb) possibly reflecting a high ge ne density in the corresponding chromosome region. Equivalent amplification of 64 sequence tagged sites spanning the corresponding region from homozyg ous +/+ and CLPG/CLPG individuals disproves the hypothesis of a major delet ion causing the CLPG mutation.