中文摘要：

目的获得粉尘螨变应原第3组分（Der f 3）的编码基因并了解其序列多态性。方法根据GenBank已公布的Der f 3核酸序列设计引物,用RT-PCR扩增获得其编码基因,插入pMD19-T载体,进行序列测定和多态性分析。结果获得粉尘螨变应原Der f 3编码基因为780bp。5株Der f 3基因cDNA克隆的核苷酸序列与参考序列（GenBankNo.AY 283291,GenBank No.D63858,GenBank No.EU312162,GenBank No.EU312163）相比,有19处cDNA序列发生突变,但有7处突变至少在3个cDNA克隆中序列一致;推导出氨基酸序列后进行比对,有11处氨基酸序列发生变化,有4处与上述7个位点相一致。结论获得了粉尘螨变应原Der f 3编码基因且证明其序列具有多态性,为进一步开展相关研究奠定了基础。

英文摘要：

Objectives To obtain the gene encoding the group 3 allergen of Dermatophagoides farinae（Der f 3） and ascertain its sequence polymorphism.Methods The total RNA of D.farinae was extracted,and the gene encoding Der f 3 was amplified by RT-PCR with primers designed in accordance with the sequence previously published in GenBank.The target gene was inserted into a pMD19-T plasmid and then sequenced and analyzed for its sequence polymorphism.Results The cDNA encoding Der f 3 had 780 base pairs（bp）.Sequence analysis showed that there were nineteen mismatched nucleotides in five Der f 3 cDNA clones in comparison to four sequences previously published in GenBank（GenBank Accession No.AY283291,GenBank No.D63858,GenBank No.EU312162,and GenBank No.EU312163）.Seven of these 19 mismatched nucleotides were conserved among three or more sequences of these nine sequences.When these nucleotide sequences were translated into amino acid sequences using Translate Tools on the ExPaSy web server,there were eleven incompatible amino acid（AA） positions.Four of these 11 incompatible amino acid（AA） positions were consistent with the 7 positions mentioned.Conclusion The gene encoding Der f 3 was obtained and displayed polymorphism,providing a foundation for further research.