The mh gene causing double-muscling in cattle maps to bovine chromosome 2.
Using a panel of 213 bovine microsatellite markers and a pedigree obtained by backcrossing double-muscled (Belgian Blue) × Friesian (non-double-muscled) cows to a double-muscled bull, a locus that accounted for all the phenotypic variation in muscling of backcrosses was mapped to chromosome 2. The locus, designated mh (muscular hypertrophy), was positioned with respect to 7 microsatellites, the closest being 2 cM from mh. The linkage relationship between mh and the markers was confirmed in 3 informative pedigrees in the Belgian Blue breed. The results confirm the autosomal recessive monogenic model for the genetic control of double muscling.