分子进化与基因组多样性（张亚平）知识库

Objective To investigate the intraspecific difference of the triose phosphate isomerase(tim) gene from Giardia lamblia ( G. lamblia). Methods Total genomic DNA of G. lambfia was extracted and partial fragments of the triose phosphate isomerase (tim) gene were amplified by polymerase chain reaction (PCR). All nucleotide sequences were analyzed by using a phylogenetic analysis, which was constructed with parsimony and Neighbor-joining (N-J) methods. Results A total of 124 variable sites (23% of all sequences detected) was defined, most of which were found at the silent sites of codons. Two similar phylogenetic trees were constructed, subdividing 16 Giardia isolates into two groups. Conclusion The genetic diversity of G. lamblia appeared to be little affected by factors of both host and geography, while natural-selection played an important role in DNA molecular evolution level of the tim gene. The tim gene may be considered a very useful genetic marker of the population genetic structure of G. lamblia.

目的探讨蓝氏贾第鞭毛虫(Giardia lamblia)磷酸丙糖异构酶基因种内差异.方法提取虫体总DNA,对所有虫株磷酸丙糖异构酶(tim)基因部分片段进行PCR扩增.测定序列后,用简约法和NJ法构建系统树进行系统发育分析.结果共有124个位点存在变异(占所有测定序列中的23%),且大多数为发生在密码子的同义突变. 两种构树方法所得二树的分枝结构相似,均将受试的16株蓝氏贾第虫分为明显的两组.结论宿主及地理因素对蓝氏贾第虫群体的遗传多样性影响不大.在DNA分子进化水平上,自然选择的影响十分显著.可将tim基因作为蓝氏贾第虫群体遗传结构一个十分有效的遗传标记.