贾第虫被认为是目前已知的最原始的真核细胞。它具有一系列令人惊讶的原始特征，但同时也存在许多争议。其中，它究竟是几倍体就是一个长期悬而未决的问题。另外，其核型也很令人困惑，有研究表明竟然在它的双核之间、不同个体和不同株之间都存在核型上的差异，并出现“非整倍体”现象。在我们通过摸索已在贾第虫上成功改进了同步化、核型分析和荧光原位杂交等技术的前提下，本项目拟对几个不同种的贾第虫进行系统的核型分析比较研究，探讨其核型究竟具有怎样的特征，在不同的种株之间又有怎样的变化规律。更重要的是，本项目拟在其核型标本的基础上，选取多个单拷贝基因为探针对其染色体进行荧光原位杂交实验，以便很直观可靠地对贾第虫的倍性进行分析，旨在明确确定贾第虫的倍性，并揭示其在此基础上发生了怎样的非整倍体化。鉴于该生物极重要的进化地位，本研究势必会对认识理解真核生物倍性的起源进化和基因组的稳定性机制等重要生物学问题具有重要意义。

Giardia is thought to be one of the earliest-branching eukaryotes on phylogenetic trees. It has lots of intriguing but puzzling features including the ploidy and karyotypes of the trophozoites. So far the ploidy of the Giardia is still unclear. Previous studies show the differences of the karyotypes can appear between the two nuclei, different cells or different strains, and the “aneuploid” is another puzzling phenomenon. Based on our modified techniques, this project is going to firstly analyze Giardia’s karyotype of different species, to see the common feature of Giardia’s karyotype, and how the karyotypes changing among Giardia. Then Fluorescence in Situ Hybridization will be used to analyze the ploidy of Giardia and the situation of “aneuploid”. Because of Giardia’s important evolutionary position, this project would expectedly contribute to our understanding of the ploidy origin and evolution and of mechanisms underlying genome stabilization in eukaryotes.