转座子是物种进化的重要推动力之一。金鱼在短期内演化出体形、体色各异的品系，是开展形态发育和进化研究极其珍贵的材料。双尾变异在动物界罕见，但在金鱼中普遍存在，转座子插入突变chordinA(chdA)基因与金鱼双尾型变异密切相关。本项目拟构建Tgf2转座子插入突变chdA基因的草金双尾型纯系，通过与野生单尾杂交获得F1代，再与双尾纯合子测交及杂合子自交获得F2代，进而研究基因-表型的相关性，鉴定出chdA突变基因的显、隐性特征；通过分析草金双尾突变纯合子自交后代性状，判定基因型与双尾突变的相关性，并研究转座子插入的敲除效果及遗传稳定性；通过开展chdA基因的过表达拯救及转座酶介导切离进行性状恢复，揭示在双尾型形成中该基因对背腹化通路的作用模式。本研究旨在探索Tgf2转座子插入失活chdA基因与金鱼双尾型突变的相关性及分子机制，以阐明转座子在物种形成和进化中的地位和作用，具有较高的理论创新性。

Transposon is one of the important driving forces in species evolution. Goldfish varieties with different body-shapes and body-colors have been artificially selected in a relatively short period of time, which are considered as precious scientific materials in genetic, developmental and evolutionary studies. Twin-tailed animals are rare in nature, but the twin-tail traits exist widely in goldfish variations. Transposon insertion of chordinA(chdA) gene impacting embryonic dorsal-ventral signal pathway is presumable as an important driving force for the formation of twin-tail type traits in evolution. Our project aims to construct pure line of twin-tail common goldfish with chdA mutation by Tgf2 transposon insertion. The twin-tail homozygote and single-tail wild-type common goldfish family were morphologically and genetically identified. Then, F1 heterozygotes were produced by hybridization of twin-tail homozygote with wild-type common goldfish. And F2 generations were constructed by backcross with twin-tail homozygote and self-crossing F1 heterozygote. In F2 generation, the correlations between the genotype and phenotype were studied and the dominant and recessive traits of twin-tail mutant genotypes were established. Moreover,the effects of transposon insertion and knockout on genetic stability in the genomic insertion site were evaluated. Finally, overexpression of chdA gene was performed to rescue the twin-tail phenotype of common goldfish. Also, the wild-type phenotype of common goldfish was tried to be recovered using the Tgf2 transposase protein or mRNA microinjection. This research aims to investigate the correlation between Tgf2 transposon insertion mutagenesis of chdA gene and the twin-tail mutant genotype in goldfish and its possible molecular mechanism. The present study expresses an innovated idea which will be helpful in clarifying possible role of transposon in speciation and evolution of animal species.