Meiotic Crossing-Over: How it Ensures Disjunction

MCB-9513231 Dawson单倍体细胞（例如，卵子和精子）由二倍体细胞通过两轮染色体分布形成，称为减数分裂。 在第一轮中，每个同源染色体对的两个成员被吸引到相反的两极。 为了使每个单倍体细胞都能以适当的拷贝数接收到所有的遗传信息，同源物的分离必须准确。 在大多数真核生物中，同源染色体之间的减数分裂交换是成功分离所必需的。在减数分裂重组中具有缺陷的突变体通常是不育的或表现出降低的育性。减数分裂交换用于在物理上连接同源物，并与称为交叉结合剂活性的活性结合，将同源物稳定地保持在一起，直到它们正确地附着在减数分裂纺锤体上并在后期I彼此迁移离开。尽管在提高减数分裂染色体分离的保真度的重要性，很少有人知道的因素，影响能力的交叉，以执行其减数分裂的作用。 研究者实验室的长期目标是促进对利用交换和其他因素保持同源物连接直到后期I的装置的全面理解，从而确保减数分裂分离。 这些实验将利用酿酒酵母作为研究生物。 这个项目的目的是确定重组事件的特点，这样做，所以不确保分离的YLps。 将进行实验以确定具有不同能力的交叉的特征，以增强分离。 将探讨重组事件的染色体定位、发生交换的序列以及减数分裂DSB与确保分离的交换的产生的关系。 这些实验旨在测试四个模型，这些模型描述了为什么交叉不能同样确保分离。 这些模型如下：1. 交叉增强分离的能力受其与端粒的距离的影响，或2。通过它与着丝粒的距离。 3. 一些序列环境允许附近的交叉以确保析取，而另一些则不允许。 4. 交叉确保分离的能力与交叉开始的方式有关。 ***

MCB-9513231 Dawson Haploid cells (e.g., eggs and sperm) are formed from diploid cells by two rounds of chromosome distribution called meiosis. In the first round, the two members of each homologous chromosome pair are drawn to opposite poles. For each haploid cell to receive all the genetic information in the proper number of copies, it is essential that this segregation of homologs be accurate. In most eukaryotic organisms, meiotic exchange between homologous chromosomes is required for this segregation to be successful. Mutants with defects in meiotic recombination are frequently sterile or exhibit reduced fertility. Meiotic crossovers serve to physically link homologs, and in conjunction with an activity referred to as chiasma binder activity, hold the homologs stably together until they are properly attached to the meiotic spindle and migrate away from each other at anaphase I. Despite the importance of crossovers in enhancing the fidelity of meiotic chromosome segregation, little is known about the factors that influence the ability of crossovers to perform their meiotic role. %%% The long term goal of the investigator's laboratory is to contribute to a comprehensive understanding of the apparatus which utilizes crossovers and other factors to keep homologs joined until anaphase I, thus ensuring meiotic disjunction. These experiments will utilized the yeast Saccharomyces cerevisiae as a research organism. The objective of this project is to determine the characteristics of recombination events which do and so not ensure the disjunction of YLps. Experiments will be performed to determine the characteristics of crossovers with different abilities to enhance disjunction. The chromosomal location of recombination eventq, t he sequences in which crossovers occur, and the relationship of meiotic DSBs to the generation of crossovers which ensure disjunction will be explored. The experiments are designed to test four models that describe why crossovers are not equally able to ensure disjunction. These models follow: 1. The ability of a crossover to enhance segregation is influenced by its distance from the telomere, or 2. by its distance from the centromere. 3. Some sequence environments allow nearby crossovers to ensure disjunction while others do not. 4. The ability of a crossover to ensure disjunction is related to the manner in which the crossover is initiated. ***