Association of GnRH1 Gene with Growth Traits in Two Breeds of Sheep

The present study was conducted to identify the associations between the genetic polymorphisms of GnRH1 gene and growth traits in Awassi and Karakul breeds of sheep. Two GnRH1 amplicons of 313 bp and 323 bp were designed to cover exon 1, exon 2, and their flanking regions, respectively. Genotyping experiments were performed using PCR-SSCP and DNA sequencing. No polymorphism was observed in 323 bp amplicons, while two SSCP-banding patterns were detected in 313 bp amplicons with the presence of two genotypes (AA and AB). Two novel mutations in AB genotype were observed, namely 5′-UTR:50 A > C and intron1:264 G > C. In addition to these detected genotypes, results indicated that several growth traits were significantly associated with breed, sex, and dam-age in the first 6 months of birth. However, a tendency of individuals with AA genotype to exert better performance in the majority of measured growth traits than individuals with AB genotype was also observed. With the advent of the month-9 and onward, this tendency developed to be significant (P < 0.05), in which the association of all growth traits with the GnRH1 genotypes was dominated over other factors. Furthermore, more significant associations were observed in the month-12, in which individuals with AA genotype had higher growth traits measurements than individuals with AB genotype (P < 0.01). In conclusion, we detected a tight linkage between the polymorphisms of the GnRH1 gene and growth traits at sexual maturity. Therefore, this study strongly suggests the GnRH1 gene as a new candidate in marker-assisted selection for growth traits in sheep.