Identification of the Single Base Change Causing the Callipyge Muscle Hypertrophy Phenotype, the Only Known Example of Polar Overdominance in Mammals

Marker informativeness among heterozygous (by progeny testing)CLPG Dorset rams used in the mutation discovery panel. Asterisks on the top row (Map) indicate relative positions of markers used to construct the chromosome 18 linkage group. The arrow (position 86–87 cM) indicates relative position of the CLPG locus. Markers heterozygous are presented as asterisks for each ram. All rams were genotyped for all markers on the chromosome 18 map. Regions of the linkage group for each ram not flanked by an informative marker are indicated by dotted lines. Of particular interest, rams 198812900 and 199112900 exhibit marker homozygosity in the critical region containingCLPG.