A 2ND-GENERATION LINKAGE MAP OF THE SHEEP GENOME

A genetic map of Ovis aries (haploid n = 27) was developed with 519 ma rkers (504 microsatellites) spanning similar to 3063 cM in 26 autosoma l linkage groups and 127 cM (female specific) of the X Chromosome (Chr ). Genotypic data were merged from the IMF flock (Crawford et al., Gen etics 140, 703, 1995) and the USDA mapping flock. Seventy-three percen t (370/504) of the mic microsatellite markers on the map are common to the USDA-ARS MARC cattle linkage map, with 27 of the common markers d erived from sheep. The number of common markers per homologous linkage group ranges from 5 to 22 and spans a total of 2866 cM (sex average) in sheep and 2817 cM in cattle. Marker order within a linkage group wa s consistent between the two species with limited exceptions. The repo rted translocation between the telomeric end of bovine Chr 9 (BTA 9) a nd BTA 14 to form ovine Chr 9 is represented by a 15-cM region contain ing 5 common markers. The significant genomic conservation of marker o rder will allow use of linkage maps in both species to facilitate the search for quantitative trait loci (QTLs) in cattle and sheep.