effect of allelic polymorphism in exon 3 of leptin gene on production traits in naeini sheep breed

identification of effective major genes releted with energy balance, milk production, fertility, immunity, as well as feed consumption constitutes some of the most important and strategic objectives in animal breeding and genetics researches. among the major genes, leptin is one of the largely effective ones the polymorphism of which is closely related with important economic traits in livestock. throughout this study, 100 blood samples were randomly collected from naeini sheep breed. dna was extracted using modified salting out method and polymerase chain reaction employed for amplification of a fragment of 275 bp length from exon 3 of leptin gene. the two methods of pcr-sscp and dna sequencing were employed for identification of different genotypes. results showed a single nucleotide mutation of a to c in the nucleotide position of 49 (in the amplified fragment) indicating a type of silent mutation. the frequency of each a and c alleles and of the two aa and ac genotypes were determined at 0.73 and 0.27, respectively. in the course of this research work, the observed effect on growth and wool production traits was also evaluated. the birth weight in sheep with ac genotype was higher than that in animals with bb genotype (p< 0.01), but there was no other significant effect of the observed genotypes on the other studied traits. it can be concluded that in the case of repeated results obtained from further research in the future studies, (of  higher sample sizes) it may be possible to use either this marker site or other sites (relevant to leptin gene) in selection programs as based on molecular dna markers.