Polymorphism Analysis On Partial Sequence Of Obese Gene In Different Pig Breeds (Lines) By PCR-SSCP

The lean meat percentage is one of'the important traits in pig breeding. Obese gene,which contains three exons and two introns,is a newly cloned gene,whose product-leptin functions as factor regulating fat content and body weight. The ob gene may be the major gene that influences the fat deposition and lean meat percentage. The study on it will have theoretical and practical significance.In this study,we analyzed the polymorphism of porcine ob cDNA among different breeds including Landrace,Duroc,Min pig,Yorkshire,double-muscled Yorkshire,Sanjiang pig,Wild boar and Cross bred pig by PCR-SSCP. We designed three pairs of primers according to the ob cDNA sequence obtained from Genbank database to amplify the first two exons and analyze them by SSCP. We have found a T to C transversion in the second exon. So there were three genotypes in different porcine breeds Which were named AA,AB and BB respectively. In Min pig,there were only genotype of BB,while no allele B was detected in double-muscled Yorkshire;in other breeds three genotypes all existed. And the frequencies of these genotypes had difference among breeds.In breeds of Min pig,Sanjiang pig,Duroc,Yorkshire Landrace,double-muscled Yorkshire. The frequencies of A gene increased progressively,and the lean meat percentage in these breeds also rised in this order. Sanjiang pig,Duroc,Yorkshire pig,Landrace were all bred to improve lean meat percentage and the double-muscled Yorkshire had the highest percentage,while Min pig was bred for fat mass. A gene frequencies of wild boar and cross bred pig was between that of fat pigs and lean meat pigs. There was a trend that the distribution of A gene is highly relative to the lean meat percentage on the one hand,on the other hand it was linked to selected direction. So the allele A could be used as. selective marker of lean meat percentage in pig breeding.