Vahideh Rezaei - Department of Animal Science, Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman, Iran.
Ali Esmailizadeh - Department of Animal Science, Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman, Iran.
Ahmad Ayatollahi Mehrgardi - Department of Animal Science, Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman, Iran.
Mostafa Dehghani Qanatqestani - Department of Animal Science, Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman, Iran.

The main purpose of this study was to assess the presence of the previously reported single nucleotide polymorphisms (SNPs) in the sheep growth differentiation factor ۹ (GDF۹) and bone morphogenetic protein ۱۵ (BMP۱۵) genes and their association with litter size at lambing in Iran-Black sheep breed. Blood samples were taken from ۱۲۰ Iran-Black ewes. DNA extraction was conducted using a modified salting-out method. DNA fragments with sizes of ۴۶۲bp and ۱۴۱bp for the GDF۹ and BMP۱۵ genes were amplified using PCR with specific primers, respectively. The PCR-RFLP approach was adopted for detecting the genotypes. The results indicated that the SNP in the exon ۲ of BMP۱۵ is a monomorphic locus in Iran-Black sheep.  However, the substitution of G to A nucleotide was determined in the GDF۹ locus. Digestion of the ۴۶۲bp PCR product from exon ۱ of theGDF۹ using the HhaI restriction enzyme produced fragments of ۵۲, ۱۵۶, and ۲۵۴bp. However, DNA fragments containing the A nucleotide yielded only two fragments (۵۲ and ۴۱۰bp). The heterozygous animals for this mutation in GDF۹ locus had fragments of all four sizes (۵۲, ۱۵۶, ۲۵۴, and ۴۱۰bp). The frequency (۰.۷۵) of the wild type allele (+) in GDF۹ locus was higher than the frequency (۰.۲۵) of mutant allele (G). The observed frequencies for the GG, G+ and ++ genotypes were ۰.۰۵, ۰.۴۰ and ۰.۵۵, respectively.  The association results indicated that the mutation of GDF۹ gene has a substantial impact on lambing rate and the Iran-Black ewes with the GG and G+ genotypes had higher lambing rate than those with the ++ genotype. Thus, a gene assisted selection program to improve lambing rate in this breed can be designed based on the GDF۹ gene mutation. Key words: BMP۱۵, GDF۹, Litter Size, Iran-Black Sheep

BMP۱۵, GDF۹, Iran-Black sheep, lambing rate