GENETIC ORGANIZATION OF TETRAHYMENA

长期目标包括：（1）基因定位， 嗜热四膜虫高度分化的体细胞核， 可以研究分化机制，（2）详细了解 包括影响减数分裂的环境和遗传因素， 染色体配对和重组，（3）涉及的遗传因素 在核糖体生物合成中。 所有拟议的研究都利用了 将生殖细胞和躯体功能分离到两个不同的细胞核中， 四膜虫 具体目的包括：（1）缺失菌株的分离 臂的染色体，并含有新的协会染色体臂。 这将通过使用复杂的多单体的杂交来完成。 的 十字架将在防止产生新的 体细胞核，因此允许细胞的存活恢复， 缺体胚细胞核。 (2)基因图谱的创建基于 有丝分裂重组。 这将通过搜索诱导的 特定标记的纯合性。 这是必要的，因为减数分裂 重组太活跃而不能在染色体上定位基因。 紫外线辐射对突变体影响的比较测量 形成和有丝分裂重组。 (3)研究 在编码核糖体RNA（rDNA）的基因中的减数分裂重组。 这些研究利用了核糖体DNA的单拷贝结构， 胚核 耐药突变体和影响核糖体的突变 确认将被隔离。 rDNA中的突变将通过 与携带一种基因的菌株杂交， 体细胞核，并将定位到特定的核糖体亚基，通过在 体外试验 它们将通过DNA序列分析被精确定位。 具体 该基因中的突变组合将用于测量 控制细胞中减数分裂重组的数量，然后在细胞中 不寻常的环境和携带不寻常的核型（单体和 缺体）。 这项研究应提供详细资料，说明如何 环境和基因型可以影响减数分裂的各个方面。 (4)改进 将开发冷冻和储存这些复杂细胞的方法 基于长期饥饿的影响。

The long term objectives include (1) a mapping of genes in the germinal and highly differentiated somatic nuclei of Tetrahymena thermophila so that mechanisms in differentiation can be studied, (2) a detailed understanding of meiosis, including environmental and genetic factors that influence chromosome pairing and recombination, and (3) the genetic factors involved in ribosomes biosynthesis. All of the proposed studies exploit the separation of germinal and somatic functions into two different nuclei in Tetrahymena. Specific aims include: (1) The isolation of strains missing arms of chromosomes, and containing novel associations of chromosome arms. This will be done by crosses using complex, multiple monosomics. The crosses will be done in circumstances that prevent the production of new somatic nuclei, and therefore allow the viable recovery of cells with nullisomic germinal nuclei. (2) The creation of a genetic map based on mitotic recombination. This will be done by searching for induced homozygosity of specific markers. It is necessary since meiotic recombination is too active to allow mapping of genes on chromosomes. Measurements comparing the effect of ultra violet radiation on mutant formation and mitotic recombination will be performed. (3) A study of meiotic recombination in the gene coding for the ribosomal RNA (the rDNA). These studies exploit the single copy organization of the rDNA in the germinal nucleus. Drug resistant mutants, and mutations effecting ribosome confirmation will be isolated. Mutations in the rDNA will be identified by crosses with strains carrying a gene that distorts its amplicication in the somatic nucleus, and will be localized to specific ribosomal subunits by in vitro testing. They will be pinpointed by DNA sequence analysis. Specific combinations of mutations in this gene will be used to measure the exact amount of meiotic recombination in control cells, and then in cells in unusual environments and carrying unusual karyotypes (monosomics and nullisomics). This study should provide detailed information on how environment and genotype can influence aspects of meiosis. (4) Improved methods of freezing and storage of these complex cells will be developed based on the effects of prolonged starvation.