鲤鱼6个群体间MHCⅡB基因第3外显子的多态性分析

Polymorphisms of exon 3 of MHC class ⅡB gene in six populations of commom carp(Cyprinus carpio)

根据已克隆的鲤鱼MHC Ⅱ B基因序列,设计1对特异性引物,采用PCR-SSCP方法对6个鲤鱼群体MHC Ⅱ B基因第3外显子108 bp扩增片段进行多态性分析,结果共获得7种基因型（A-G）,其中基因型为B型的个体数占所有群体总个体数的47.45%,且分布于所有群体,其它6种基因型出现频率范围为1.1%~17.15%。回收不同基因型的片段并测序,经比对共发现4个碱基多态位点和3个氨基酸多态位点。易捕鲤和大头鲤两群体中各发现4个突变位点（占3.7%）;松荷鲤、松浦鲤和德国镜鲤群体各发现3个突变位点（占2.7%）;松浦镜鲤群体仅发现2个突变位点（占1.8%）。用Popgene软件计算每个群体不同位点的杂合度和多态信息含量（PIC）,6个鲤鱼群体的观测杂合度（Ho）最大值为0.746 4,最小值为0.103 7;多态信息含量为0.062 3~0.360 9。该研究将为今后深入研究鲤鱼MHC基因多态性及与鲤鱼抗病新品种的选育提供理论依据。

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.