DISSERTATION RESEARCH: Evolutionary genetics of crossover rate differences across the Drosophila phylogeny

减数分裂是一种特殊的细胞分裂形式，最终产生配子（即精子和卵子）。该项目将研究减数分裂期间发生的重组，即成对染色体之间的遗传信息交换。该项目具有广泛的教育和社会影响，包括为本科生和高中生提供经典遗传学、基础分子生物学和进化生物学方面的培训机会。此外，实验系统的可移植性有助于中学生参与暑期科学教育项目的推广工作。该研究具有潜在的社会影响，包括人类健康，因为减数分裂中断会导致不育和后代染色体数目异常。在减数分裂的第一阶段发生的重组有两个重要功能。首先，重组确保了适当数量的染色体分布到配子细胞中。其次，重组产生新的基因组合，这对后代有潜在的好处。尽管有这些好处，重组也有风险，因为它可以产生有害的重复和删除突变。因此，重组的频率可能会进化，以平衡重组的好处和风险。使用果蝇属，本研究将调查染色体重组事件的频率和物理位置如何在物种之间进化。特别是，本研究将探讨减数分裂基因的快速分子进化如何导致在果蝇物种进化树上观察到的重组率差异的进化。该项目将使用候选基因方法研究快速进化的mei-218基因，该基因负责黑腹果蝇和毛里求斯果蝇之间的大部分交叉率差异。该项目将测试mei-218的分子进化对果蝇系统发育中重组率变化的影响程度，使用分子进化分析来测试多个果蝇谱系中mei-218的反复阳性选择历史。该项目还将使用转基因方法来分析来自多个果蝇物种的mei-218基因的表型效应。

Meiosis is a specialized form of cell division that ultimately produces gametes (i.e., sperm and egg). This project will examine recombination, the exchange of genetic information between paired chromosomes, that occurs during meiosis. The project has broad educational and societal impacts, including opportunities to train undergraduate and high school students in classical genetics, basic molecular biology, and evolutionary biology. Furthermore, the portability of the experimental system facilitates outreach efforts involving middle school students participating in summer programs in science education. The research has potential societal impacts including human health as meiotic disruptions contribute to infertility and aberrant chromosome number in progeny. The recombination that occurs during the first stage of meiosis serves two important functions. First, recombination ensures the distribution of the appropriate number of chromosomes into gamete cells. Second, recombination generates novel genetic combinations that are potentially beneficial to the progeny. Despite these benefits, recombination has risks because it can generate deleterious duplication and deletion mutations. The frequency of recombination may therefore evolve to balance the benefits of recombination against its risks. Using the fly genus Drosophila, this research will investigate how the frequency and physical placement of recombination events along chromosomes has evolved between species. In particular, this research will investigate how the rapid molecular evolution of a meiosis gene has resulted in the evolution of differences in recombination rate observed across the evolutionary tree of Drosophila species. The project will investigate the rapidly evolving mei-218 gene which is responsible for most of the crossover rate difference between Drosophila melanogaster and Drosophila mauritiana using a candidate gene approach. The project will test the degree to which molecular evolution at mei-218 contributes to the variation in recombination rates across the Drosophila phylogeny using a molecular evolutionary analysis to test for histories of recurrent positive selection at mei-218 in multiple Drosophila lineages. The project will also use a transgenic approach to assay the phenotypic effects of the mei-218 gene from multiple Drosophila species.