Hha I enzyme reveals genetic polymorphisms at the second exon of porcine-growth-hormone gene

A 230-bp fragment, which contains the second exon of the porcine-growth-hormone (pGH) gene, was amplified using DNA samples of 30 Erhualian, 36 Pietrain, and 30 German Landrace pigs. Polymorphic restriction sites for Hha I were identified at bases 506-509 and 555-558, respectively. The digestion yields a single 230-bp fragment, two fragments of 173 and 57 bp, two fragments of 106 and 124 bp, or three fragments of 124, 57, and 49 bp, respectively. The allele frequencies are significantly different (p < 0.01) between Chinese pigs and European pigs, when each or both restriction sites with Hha I were considered. The sequence analysis indicated that a C/T substitution at position 507 caused the polymorphisms at 506-509, while both a G/A substitution at position 555 and a C/A substitution at position 556 resulted in the polymorphic bands at 555-558. These mutations caused amino-acid substitutions in the amino-acia sequence of pGH.