Polymorphisms of exon 3 of MHC class IIB gene in six populations of commom carp(Cyprinus carpio)
In this study,a pair of specific primers,designed according to the doned common carp MHC Ⅱ B gene sequences,was used to analyze the uniform fragment of 108 bp of exon 3 of MHC Ⅱ B gene by PCR-SSCP(polymerase-chain-reaction-single-strand-conformation polymorphism) in six common carp populations.The re-sult showed that seven genotypes(A-G) were acquired in the populations.The most common genotype was of genotype B that presented in all populations and accounted for 47.45%.The ratio of other genotypes varied from 1.1% to 17.15%.Four variable nucleotide positions and three variable amino acid positions were detected after fragments of different genotypes were recycled and sequenced.The populations of Yibu common carp and Big-head common carp had four(3.7%) variable nucleotide positions.Three(2.7%) variable nucleotide positions were found in the populations of Songhe common carp,Songpu common carp and German mirror common carp.The population of Songpu mirror common carp had only two(1.8%) variable nucleotide positions.Observed het-erozygosity(Ho),expected heterozygosity(He) and polymorphism information contents(PIC) were determined.The observed heterozygosity value(Ho) was from 0.1037 to 0.7464;the expected heterozygosity value(He) was from 0.0652 to 0.4825 and the PIC value was from 0.0623 to 0.3609,respectively.The data may be of great help in the study of MHC gene polymorphisms and the selected breeding of disease resistance in common carp.