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)。这个项目将研究减数分裂过程中发生的重组，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，包括培训本科生和高中生古典遗传学、基础分子生物学和进化生物学的机会。此外，实验系统的可移植性促进了中学生参加科学教育暑期项目的外展努力。这项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孕不育和后代染色体数量异常。发生在减数分裂第一阶段的重组有两个重要的功能。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，重组产生了新的基因组合，这些组合可能对后代有利。尽管有这些好处，重组还是有风险的，因为它会产生有害的复制和缺失突变。因此，重组的频率可能会发生变化，以平衡重组的好处和风险。利用果蝇属，这项研究将调查重组事件的频率和沿染色体的物理位置是如何在物种之间进化的。特别是，这项研究将调查减数分裂基因的快速分子进化如何导致在整个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，该基因是导致黑腹果蝇和毛果蝇交叉率差异的主要原因。该项目将使用分子进化分析来测试在多个果蝇谱系中，位于mei-218的分子进化对果蝇系统发育中重组率的差异的贡献程度。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.