MOLECULAR CHARACTERIZATION OF OVINE ALPHA-INHIBIN ACTIVIN, BETA(A)-INHIBIN/ACTIVIN AND BETA(B)-INHIBIN/ACTIVIN ALLELES/

The ovine inhibin/activin genes were investigated as QTL candidates fo r litter size. An RFLP study with five breeds of differing fecundity i dentified 4 INHA, 2 INHBA and 2 INHBB alleles. The frequency of a TaqI INHBA allele was correlated with the average litter size of the inves tigated breeds (n=40-169). Statistical analysis of lambing records fro m East Friesian Milksheep (n=146) yielded significant INHBA gene effec ts on litter size. Sequence analysis of PCR products identified severa l nucleotide substitutions in coding regions of the INHBA gene, some o f which change the predicted amino acid sequences. Genomic cloning and sequence analyses of three copies each of all three inhibin/activin g enes identified additional INHBA and INHBB alleles, and revealed furth er sequence polymorphism in coding regions and regulatory elements. Al l three genes were mapped by in situ hybridization. This excluded INHB B as the site of the Fec(B) mutation. For INHA and INHBA, the assignme nts were confirmed by linkage mapping.