RESUMEN
Single nucleotide polymorphisms (SNPs) in partial 5' regulatory region of the insulin-like growth factor 2 (IGF2) gene were studied by DNA sequencing in 60 pigs from the Wuzhishan, Diannan small-ear, Xiang, Meishan and Large White pig breeds. Thirteen SNP sites were detected, including one transversion at T6029A, 4 A<---->G transitions (A5976G, G13520A, G13563A and G13669A) and 8 C<---->T transitions (C5872T, C5888T, C6010T, C6037T, C6043T, C6063T,C6112T, C6164T). These 13 SNPs formed 23 composite genotypes. The gene, genotype and composite genotype frequencies of every SNP site in the whole group and in each breed were calculated. Results showed that the predominant allele in 3 miniature pig breeds was G, T and A at A5976G, C6164T and G13669A sites respectively, but the A-C-G allele was pre-dominant in Meishan and Large White breeds. Moreover, H15 and H19 were the characteristic composite genotype for the large versus the miniature breeds, respectively. In addition, the C5888T SNP was analyzed in 123 Wuzhishan pigs by the PCR-RFLP method. Results showed that the predominant allele was C, and the predominant genotype was CC. chi2-test results indicated that the Wuzhishan pig breed was at Hardy-Weinberg equilibrium with respect to this SNP. These results provide the miniature pig breeds such as the Wuzhishan pig with certain genetic references on the regulation of growth and development, and the mechanism of its dwarfism.