Determination of the effects of some single nucleotide changes in the GHSR gene locus on growth characteristics in awassi and cet sheep

This thesis investigates the effects of the GHSR gene locus on growth traits in İvesi and Çet sheep. The aim of the study is to determine how different polymorphisms of the GHSR gene contribute to variations in growth-related phenotypic traits in sheep and to elucidate the genotype-phenotype relationships. The GHSR gene plays a key role in regulating growth hormones, and polymorphisms identified in the intronic regions of this gene may influence growth performance in sheep. The study was conducted on two different sheep breeds, İvesi and Çet, and analyzed the effects of the c.1797G>T and c.3554T>G polymorphisms in the GHSR gene on growth traits in these breeds. A total of 60 İvesi sheep and 60 Çet sheep were used in the study, and the genotypic distributions and their effects on various growth traits were evaluated. In İvesi sheep, the c.1797G>T polymorphism was found to have significant effects on live weight and chest depth. Sheep with the GT genotype exhibited higher live weight and chest depth values compared to the other genotypes. Additionally, the c.3554T>G polymorphism was found to influence live weight and body length, with the TG genotype being advantageous in both traits. In Çet sheep, the c.1797G>T polymorphism was found to significantly affect body length, with sheep carrying the GT genotype having longer body lengths. Furthermore, the c.3554T>G polymorphism showed a significant effect on chest width, with the TG genotype being advantageous in this trait. The results demonstrate that the GHSR gene is significantly associated with certain growth traits in both İvesi and Çet sheep, with individuals carrying the GT genotype generally showing better growth performance. However, no significant differences were observed among genotypes for other growth traits in both sheep populations. These findings support the potential impact of the GHSR gene on growth traits and highlight the importance of considering this gene in future genetic improvement programs. This study provides valuable insights for enhancing genetic selection programs in sheep breeding and developing GHSR gene-based strategies. A better understanding of the impact of genetic variation on growth performance can contribute to more efficient and successful outcomes in sheep breeding.