Abstract:
Baluchi sheep is considered as the most common breed in Iran, constituting about 30%
of total sheep population, approximately 15 million heads. This research was designed to
study the incidence of mutation in two loci of IGF-I (Exon 3) and ADRB3 (Intron) along
with their association with body weight traits in Baluchi sheep population. Following
DNA extraction from 190 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 0.89, 0.11,
respectively in IGF-I locus. As for ADRB3, two patterns corresponding with two
genotypes (their frequencies mentioned in parentheses) of AA (0.85) and AB (0.15) were
identified. One SNP change was observed in ADRB3, and one in IGF-I. A previously
reported SNP was detected in exon 3 of IGF-I. The effects of IGF-I and ADRB3
polymorphism on the corrected phenotypes for body weight at birth (BW), weaning
(WW), 6 months of age (6MW), 9 months of age (9MW) and 12 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 ADRB3, the
genotype AA was found out to exert a significant positive effect on 6MW (AA, 30.20±1.85
kg day-1; AB, 27.67±1.98 kg day-1; P<0.05).
Keywords: Baluchi sheep, β3-Adrenergic Receptors (ADRB3), Insulin-like Growth Factor
(IGF-I), PCR-SSCP, Polymorphism.
