Polymorphism of the growth hormone (GH) gene and its association with growth traits in the Kilakarsal breed of sheep

The goal of this study was to investigate the single nucleotide polymorphism of the growth hormone gene and its association with growth traits in the Kilakarsal breed of sheep. Polymerase Chain Reaction - Restriction Fragment Length Polymorphism (PCR-RFLP) of the growth hormone gene (422 bp) with HaeIII restriction enzyme revealed an A781G transition mutation at the exon 2 and the existence of two genotypes, viz., AA (366 bp and 56 bp) and AB (422 bp, 366 bp and 56 bp). The occurrence of the B allele is due to the A781G transition in the exon 2 of the growth hormone gene, which causes an amino acid change from Serine to Glycine. The genotype BB was absent in the Kilakarsal sheep population. The absence of the BB genotype at the A781G locus of the growth hormone gene in the Kilakarsal sheep population indicates that the natural selection process might be acting against this particular genotype through reduced viability or early embryonic death. Further, the statistical analysis revealed the significantly higher yearling weight of the AB than the AA genotype (P=0.038), and an appreciable difference of 1.40 kg in 9-month weight. The highly significant (P<0.001) Chi-square value (29.94) showed that the population is not the under Hardy-Weinberg equilibrium. This indicates that molecular markers associated with body weight should be explored for their use in marker assisted selection in Kilakarsal population.