THE OVINE CALLIPYGE LOCUS - A PARADIGM ILLUSTRATING THE IMPORTANCE OFNON-MENDELIAN GENETICS IN LIVESTOCK

An inheritable muscular hypertrophy was recently described in sheep an d shown to be determined by the callipyge (CLPG) gene mapped to ovine chromosome 18. We demonstrate in this work that the callipyge phenotyp e is characterized by a non-Mendelian inheritance pattern, referred to as polar overdominance, in which only heterozygous individuals having inherited the CLPG mutation from their sire express the phenotype. Th e possible role of parental imprinting in the determinism of polar ove rdominance is envisaged.