Genetic Polymorphism Research Of GH And GHR Gene And Correlation Analysis On Carcass Quality Traits In Red Steppes

Growth hormone(GH) plays a key role on the growth, development,feed conversion rate,cutability rate,controlling and regulating metabolism and physiological processes as well as other immune response. In recent years, as the candidate gene of carcass traits, milk production, growth and development traits, the research was more and more. But, to play its biological function, growth hormone must combine with its receptor (GHR), result in receptor dimerization, activate information channel, stimulate signal transduction pathway of GH, so that GH plays biological function on target cells.In this study, Red Steppes were used as experimental population. The polymorphisms of the GH and GHR genes was detected by PCR-SSCP (single-strand conformation polymorphism) method, fragments of the SNP was selected as carcass traits of genetic markers for the Red Steppes and analyzed the genetic correlation between the polymorphisms and carcass quality traits was analyzed by using general linear model (GLM),laying a founding for the study of germplasm characteristics, providing a theoretical basis for its ultra-early selection and genetic improvementThe results of the genetic polymorphism research of GH,GHR gene and the association between genetic markers and performancetraitswere were as follows:The polymorphic PCR-SSCP sites in the intron3 of the bovine growth hormone (GH) were examined in Red Steppes,The results showed that two alleles, A, and B, three genotypes, AA,AB, and BB, were detected in the intron3 of the GH gene. The polymorphism fragments were cloned and sequenced. The polymorphisms of the intron3 were caused by T→C transition at 1435bp position and A→G at 1658bp position. The Chi-square test for goodness of fit showed that the frequencies of the intron3 genotypes in the population of Red Steppes didn't agreed with Hardy-Weinberg equilibrium.The genetic correlations were obtained between genotypes of the intron4 of GH gene and carcass traits by the least square analysis.The results indicated that different GH genotypes were not significantly affected carcass quality traits(P>0.05).Average small intestine length for BB genotype was significantly higher than that for AB and BB genotype(P<0.05).The polymorphism of PCR-SSCP was found in the 4rd intron of the bovine growth hormone (GH), which caused by C→A at 1918bp position. The polymorphic sites didin't have significant affect on carcass quality traits.The polymorphic PCR-SSCP sites in the exon5 of the bovine growth hormone (GH) were examined , which were caused by A→C transversions at 2291b position , T→C transition at 2386bp position. This locus was at Hardy-weinberg equilibration.The polymorphism of PCR-SSCP was found in the 3'UTR of GH gene, which were caused by C→T transition at 2619bp position, C→G transversions at 2639bp position. HaeIII add a restriction site. The polymorphic loci at the3'UTR of GH gene had a positive relation with average body weight,live weight before slaugter, kidney fat weight, cutability weight, carcass weight, ribeye area(P<0.05),B allele was dominant allele, individuals with genetype BB at 3'UTR of GH gene had significantly higher body weight, weight before slaugter, kidney fat weight, cutability weight, carcass weight, ribeye area.A new polymorphism of PCR-SSCP was found in the 5'UTR of the bovine growth hormone (GH), which caused by A→G at 431bp position. The polymorphic sites didin't have significant affect on carcass quality traits. Average body weight, weight before slaugter, kidney fat weight, carcass weight, bone weight, small intestine weight of individual with genotype AB was significantly higher than those with genotype BB.By detecting the polymorphic PCR-SSCP sites in the exon8 of GHR,the result shows: Red Steppes population lack individualof pure genetype BB, genetic homozygosity is high,genetic heterozygosity is low, this may be relavent with the genetic background and small sample.The relationship of polymorphic loci at the exon10 of GHR gene with carcass quality traits: B allele was dominant allele, BB genetype was dominant genetype and this locus wasn't at Hardy-weinberg equilibration(P<0.001).The polymorphism of exon10 of GHR gene was caused by A→G transition at 41bp position and C→T transition at 70bp position, led histidine (H) into arginine (R), arginine (R) into cysteine (C),alkaline amino acids into polar neutral amino acids. Led K alleles into L,the changes of amino acid polar and the increas of new functional groups - SH may affect conformational space and function of growth hormone(GH).Average fat coverage percentage with genotype AB,BB was significantly higher than those with genotype AA. Average ribeye area of individual with genotype AA was significantly higher than those with genotype BB(P<0.05).Therefore, it could be preliminarily deduced that GH and GHR gene may be the major genes which associated with carcass traits in Red Steppes'carcass traits.