Polymorphism of IGF-I and ADRB۳ Genes and Their Association with Growth Traits in the Iranian Baluchi Sheep

Baluchi sheep is considered as the most common breed in Iran, constituting about ۳۰% of total sheep population, approximately ۱۵ million heads. This research was designed to study the incidence of mutation in two loci of IGF-I (Exon ۳) and ADRB۳ (Intron) along with their association with body weight traits in Baluchi sheep population. Following DNA extraction from ۱۹۰ Baluchi sheep, two pairs of primers were designed to amplify each gene. PCR-SSCP (Single-Strand Conformation Polymorphism) and DNA sequencing were employed to detect polymorphism of the mentioned genes. Two banding patterns were detected for IGF-I locus. The frequencies of AA, AB were recorded as ۰.۸۹, ۰.۱۱, respectively in IGF-I locus. As for ADRB۳, two patterns corresponding with two genotypes (their frequencies mentioned in parentheses) of AA (۰.۸۵) and AB (۰.۱۵) were identified. One SNP change was observed in ADRB۳, and one in IGF-I. A previously reported SNP was detected in exon ۳ of IGF-I. The effects of IGF-I and ADRB۳ polymorphism on the corrected phenotypes for body weight at birth (BW), weaning (WW), ۶ months of age (۶MW), ۹ months of age (۹MW) and ۱۲ months of age or Yearling Weight (YW) were examined using least square methods. No significant association was detected between the polymorphism of IGF-I and body weights. As for ADRB۳, the genotype AA was found out to exert a significant positive effect on ۶MW (AA, ۳۰.۲۰±۱.۸۵ kg day-۱; AB, ۲۷.۶۷±۱.۹۸ kg day-۱; P<۰.۰۵).

Keywords:

Baluchi sheep , β۳-Adrenergic Receptors (ADRB۳) , Insulin-like Growth Factor (IGF-I) , PCR-SSCP , Polymorphism