Genetic polymorphisms and genetic effects of IGF2 gene in pigs
Single nucleotide polymorphisms of the exon7, 8, 9 of the porcine IGF2 gene were tested using PCR-SSCP. Genetic effects of the IGF2 gene on birth weight, weaning weight, six-month weight and six-month backfat thickness were analyzed. On the basis of the published DNA sequence (AY044828) of the porcine IGF2 gene, three pairs of primers were designed, and one polymorphism, three genotypes were found in the PCR product amplified with Ex8 primers. C-->T transition at 53 site of exon8 was detected by sequencing the homozygotes. The results showed that: firstly, the genotype distribution was not consistent among the different pig breeds. No significant differences (P > 0.05) were found in the genotype distribution when compared the Landrace with the Large White , the Laiwu with the Dapuliang, and the Yimeng with the Licha Black pig breeds, whereas significant differences (P lt; 0.01) were found among other tested pig breeds in the genotype distribution. Secondly, on the basis of the fixed effect model, significant differences (P lt; 0.05) were found in birth weight and six-month backfat thickness, whereas no significant differences (P > 0.05) existed in weaning weight and six-month weight. Thirdly, using least square analysis, it was shown that individuals of the BB genotype have significantly lower (P lt; 0.05) birth weight than those of AA and AB genotypes, with the order being AB > AA > BB ; Individuals of the AA genotype have significantly lower (P lt; 0.05) six-month backfat thickness than those of AB and BB genotypes, with the order being BB > AB > AA. These results suggest that IGF2 gene has significant effects on individual birth weight and backfat thickness. The IGF2 gene can be used in marker-assisted selection to accelerate the breeding progress.