减数分裂交叉重组是减数分裂的核心事件，因为它是保证染色体正确分离的关键，也是引起物种遗传多样性的前提。但是对于交叉重组的调节及其机制的研究还不够深入。通过对相关的数据进行全面地分析，我们发现在同一物种的减数分裂细胞中存在如下的关系：较大的细胞具有较大的细胞核；较大的细胞核中每一条染色体的轴都较长。而且由于较长的染色体轴具有较高的交叉重组频率。据此，我们推测较大的细胞具有较高的交叉重组频率。与该推测相符合，我们还发现在同一细胞内如果一条染色体获得较多的交叉重组，其它的染色体也会获得较多的交叉重组，从而整个细胞会获得较多的交叉重组。在该项目中，我们将对上述发现进行全面的验证，并且综合利用多种技术对细胞大小和重组频率之间的关系进行全面的研究并解析其调节机制。本项目的完成，将有助于人们从整个细胞水平上理解减数分裂重组频率的调节及其机制；在实践上，提供一种利用减数分裂重组频率的极为简单和有效的方法。

Meiotic crossover recombination is essential for proper homologous chromosomes segregation and is also the basis for genetic diversity. The number and distribution of crossovers are tightly regulated, which is called crossover control, but the mechanism(s) for crossover control is poorly understood. Our unpublished results show that (1) when one chromosome axis is longer each of other chromosome axis also tend to be longer in a cell, i.e. there is coordinated changes for all chromosome axis length in a cell and (2) similarly there is coordinated changes for the number of crossovers on all chromosomes in a cell. Because it is well known that longer chromosome axis tend to obtain more crossovers in meiosis, the coordination of crossover numbers would be the result of the coordination of chromosome axis length. Further investigation revealed that (1) larger cells tend to have larger nuclei and (2) larger nuclei tend to have longer chromosome axis on each chromosome. Thus there is the prediction that larger cells tend to have more crossovers. The overall aim of this proposal is to elucidate whether/how the size of cells control the number of crossovers. For this purpose, multiple techniques including genetic, cytogenetic and molecular techniques and so on will be applied for more comprehensive analysis to confirm above new discoveries and to directly investigate the relationship between the size of cells and the number of crossovers. The completion of this project will provide a new way for scientists to understand the mechanism(s) of crossover control and provide a more practical and a simpler way for breed improvement in both plants and animals: increase crossover recombination level to accelerate the selection of useful genetic variation and decrease crossover recombination level to stabilize selected useful genetic traits.