Analysis On Karyotype And Polymorphism Of GH And GHR Gene And Its Relationship With Growth Traits In Goose

Karyotype analysis was carried out on Siji goose, Zhedong White goose and Wanxi White goose using the peripheral lymphocyte culture technique, and the karyotype resemblance-near coefficient and evolutionary distance among three populations of goose were calculated. The exons of growth hormone (GH) gene were cloned and sequenced, and the coding sequence of goose was obtained, the single nucleotide polymorphism (SNP) of the coding region of growth hormone gene and the 3'-regulatory region of growth hormone receptor (GHR) gene was investigated in Siji goose, Zhedong White goose and Wanxi White goose by PCR-SSCP and sequence method. The frequency of genotypes and genes was calculated and the distribution of genotype frequencies among different populations of goose was compared. The polymorphism of GH and GHR Gene and its relationship with growth traits such as body weight at 1-10 week(s) of age, carcass weight, semi-eviscerated weight, eviscerated weight and so on were analyzed. The results were as following:1. The karyotypes of Siji goose, Zhedong White goose and Wanxi White goose were similar to each other. The three populations of goose had a diploid chromosomes number of 78, with 10 pairs of macrochromosomes including the sex chromosome and 29 pairs of microchromosomes; NO.1 chromosome was submetacentric chromosome, NO.2, NO.4, Z and W were metacentric chromosome, NO.3 and from NO.5 to NO.9 were telocentric chromosome. The karyotype resemblance-near coefficient among three populations of goose were high, which indicated that these populations have close genetic relationships.2. The exons of growth hormone gene were cloned and sequenced, and the coding sequence was obtained with the length of 651bp. Homologous comparision show that the identity of cds of GH gene was 91.4% between goose and chicken, and 98.5% between goose and duck, and that was 97.6% and 99.9% in amino acid sequences, respectively. Further analysis showed that the identities of cds of goose GH gene with human and mouse were 63.81% and 74.31%, and that was 52.51% and 72.81% in amino acid level, respectively.3. Four SNPs were detected in the coding region of GH gene, they were C39T and C74T mutations within exon 2, and T291C and G297C mutations within exon 4. However, except the C74T mutation, which changed the coding amino acid from alanine to valine, other mutations were slient. The result of polymorphism analysis on exon 2 showed that there were ten genotypes in Wanxi White goose, seven genotypes in Siji goose, and eight genotypes in Zhedong White goose. In Siji goose, the allele A was superior allele, the frequency of which was 0.535. In Zhedong White goose, the allele D was superior allele, the frequency was 0.524. In Wanxi White goose, the frequency of allele A, B, C and D were 0.359, 0.063, 0.339 and 0.239, respectively. The difference of the distribution of allele might relate to the growth rate of each population. The result of polymorphism analysis on exon 4 showed that there were three genotypes in three populations. In Siji goose and Zhedong White goose, the allele E was superior allele. In Wanxi White goose, the frequency of allele E and F was close. It implied that allele E was the favorable gene for reproductive traits in goose, and this gene loci might relate to reproductive performance. 4. Associated analysis on polymorphisms of exons of GH gene and growth traits showed that the polymorphic loci of exon 2 of GH gene had significant genotype effect on early body weight (the age of 1-4 weeks) and carcass traits. CC, CD and DD genotypes were favorable genotypes for early body weight and carcass traits of goose, and could be used for molecular marker-assisted selection of early body weight and carcass traits. In Zhedong White goose, the superior allele D and allele C could be favorable genes.5. One SNP (A→G) was detected in the 3'-regulatory region of GHR gene. There were three genotypes in Siji goose and Wanxi White goose, two genotypes in Zhedong White goose. In these three populations, individuals with the MM genotype were the overwhelming majority, the allele M was superior allele. However, the number of individuals with MN and NN genotype was larger in Siji goose. The distribution of genotype in Siji goose was significantly different from that of Zhedong White goose and Wanxi White goose. It might be relevant to the history and degree of breeding in goose. Zhedong White goose and Wanxi White goose had their own conservativeness.6. Associated analysis on polymorphism of 3'-regulatory region of GHR gene and growth traits showed that this polymorphic loci had significant genotype effect only on carcass traits. MM genotype was favorable genotype for carcass traits,and the superior allele M could be favorable gene.