Molecular Cytogenetical approach on Chromosome evolution in Schistosomes.

1. 用两种方法对男性曼氏血吸虫（Sm）、日本血吸虫（Sj）和奥平并殖吸虫（Po）的减数分裂交叉频率进行了估计。第一种技术（T-I）假设存在不对称末端联合，第二种技术（T-II）假设存在终止交叉。T-I法对Po、Sm和Sj的平均细胞交叉频率分别为15.27、15.25和3.0，T-II法对Po、Sm和Sj的平均细胞交叉频率分别为20.72、18.30和II.70。T-I可能比T-II提供更准确的减数分裂交叉频率。讨论了血吸虫交叉频率的分化与物种形成的关系。建立了曼氏血吸虫YAC克隆的荧光原位杂交技术（FISH）。通过FISH对100多个YAC克隆进行了定位，发现它们广泛分布于所有染色体中。一个由16个YACs组成的组合几乎覆盖了3号染色体的整个区域。这些结果表明，每条染色体的广泛组合体应该是可行的。利用FISH对桃金娘种复合体的5个分类群样本进行了rDNA的染色体定位。从结果来看，我们认为在m.p orsula复合体的祖先种群中，rDNA最初定位于中心周围的c带，并在中心裂变发生后，随着时间的推移，在c带的跳跃增加中偶然增加。

1. Meiotic chiasma frequency was estimated in male Schistosoma mansoni (Sm), Schistosoma japonicum (Sj), and Paragonimus ohirai (Po) using two methods. The first technique (T-I) assumed the presence of achismatic terminal associations and the second (T-II) assumed the occurrence of terminalized chiasmata. The T-I method yielded a mean cell chiasma frequency of 15.27, 15.25, and 3.0 for Po, Sm, and Sj, respectively, and T-II yielded 20.72, 18.30, and II.70. The T-I may provide more accurate meiotic chiasma frequency than the T-II.Relationship between differentiation of chiasma frequency and speciation in schistosomes were discussed.2. Fluorescence in situ hybridization (FISH) for YAC clones of Schistosoma mansoni was developed. Over one hundred YAC clones were localized by FISH and found to be distributed widely among all the chromosomes. An assembly of 16 YACs covered approximately the entire region of chromosome 3. These results indicate that the extensive contig assembly of each chromosome should be feasible.3. Chromosomal localization of rDNA in sample of five taxa of the Myrmecia pilosula species complex was carried out by FISH.From the results, we suggest that the rDNA in the ancestral stock of the M.pilosula complex was localized originally in a pericentromeric C-band, and multiplied by chance with time during saltatory increases in C-banding following episodes of centric fission.