To establish theoretical basis for duck breeding of disease-resistance species, genetic polymorphism analysis was conducted by PCR amplification and DNA sequencing of exon 2 in MHCⅠ gene from Putian black duck ( hereafter referred to as exon2) . Results showed that exon 2 had high degree of genetic polymorphism, whose nucleotide variance was mainly attributed to transversion, and higher rate of synonymous substitution than non-synonymous substitution. The total content of GC in exon 2 was 59%, with the highest portion coming from the 3rd codon ( 82. 7%) . Amino acid composition analysis illustrated that exon 2 had high level of hydrophobicity, which might play a significant role in maintaining the structure and function of MHC. Moreover, cluster analysis showed that Putian black duck had a closer relationship with goose, and farther with chicken.%以莆田黑鸭为材料，对其主要组织相容性复合体( MHC)Ⅰ基因外显子2进行PCR扩增和DNA测序，分析其遗传多态性及变异特征，为进一步寻求抗病分子提供依据.结果表明，莆田黑鸭MHCⅠ基因外显子2处有丰富的遗传多态性，核苷酸变异以颠换为主，同义替换率大于非同义替换率，总 GC 含量较高，为59％，其中，密码子第3位的 GC 含量最高，为82.7％.莆田黑鸭MHCⅠ基因外显子2编码的氨基酸有明显的疏水性，对维持MHC分子的结构和功能具有重要作用.聚类分析结果表明，禽类分支中，莆田黑鸭与家鹅的亲缘关系较近，与鸡的亲缘关系较远.
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