Porcine Growth Hormone Gene Polymorphisms And Effects On Growth Performance Traits

In this paper, full sequence of porcine growth hormone (pGH) gene was amplified in Large Yorkshire and Landrace by PCR. The amplification products were analyzed in sequence polymorphisms. BstXI, Apal, Hhal and Mspl polymorphisms were detected. Effects of different genotypes on some important production performance were analyzed according to the acquired data.The sequence analysis results showed that the length of pGH gene was 2107bp including five exons and four introns. A comparison with the sequence reported by Vize et. al in 1987 showed that 57bp differences were present in the full sequence, the homology between them being 97.19%. While in five exons only three base differences existed, the homology being 99.54%. Especially, in the second exon two base substitutions had been found at positions +368 and +456. At position +368(G/A), the first result was in substitution of glutamine for arginine. While the second was homonymy substitution at position +456(T/C). But only one base was substituted for at positions +1572(A/G) in the fifth exon, and the result was in substitution of arginine for histidine.The results of restriction enzyme sites indicated that there were abundant sequence polymorphisms in the full sequence of pGH gene. There was only one BstXI restriction enzyme site without BstXI polymorphisms. After digestion with Apal, the amplified 2107bp DNA segment showed five restriction enzyme sites and four alleles, resulting in fivegenotypes, AA, AC, CC, CD and BC. Distribution of four alleles had no significant difference between two breeds (P>0.05). Hhal digestion revealed ten band-types in Large Yorkshire pigs and eight band-types in Landrace pigs (P>0.05). When digested with Mspl, the amplified DNA yielded total eight band-types, six in Large Yorkshire and seven in Landrace (P>0.05).If alpha=0.1, the Large Yorkshire pigs with AC genotype had more 165 days body weight and the average daily gain during the period from 70 to 165 days than pigs with AA genotype. Differences were statistically significant (P<0.1). While in Landrace, the pigs with T band-types had more 70 days body weight and feed to gain ratio of the period from 120 to 165 days than the pigs with V band-types. Differences were statistically significant (P<0.1). There were no significantly differences in other performance traits among different genotypes or band-types (P>0.1).