Collaborative Research: Organization of Nucleotide Diversity in the Inversions of Drosophila pseudoobscura

这个项目的研究目标是测试关于基因力量的假设，这些遗传力量调节染色体改变的变异，改变基因顺序，被称为倒位。假眼果蝇第三染色体的染色体倒位在进化生物学的文献中占有突出地位超过50年。它们已被证明是研究地理变异、自然选择、基因流动和遗传漂变的一个非常有用的模型系统。这种反转似乎是适应性选择的一个明显例子，因为它们的频率随着环境的变化而变化，形成经典的曲线，并且在一些种群中存在反转频率的季节性周期。这一建议的目的是确定选择如何作用于倒位的遗传内容内和之间的d.p pseudobscura群体。本研究将通过分析均匀分布在伪斑田鼠第三染色体上的9个PCR扩增标记的核苷酸多样性来区分不同的选择模式。这9个标记将在4个跨越反转频率梯度的种群中进行测序。在过去的二十年里，分子进化的研究集中在塑造单个基因多样性的遗传力量上，而没有考虑选择是否维持染色体上连锁基因的组合。基因组中特定染色体上基因的关联是由于选择还是偶然发生的，这是一个悬而未决的问题。倒位提供了一个重要的机制，维持遗传多样性的关联分布在染色体的长距离。这个项目将提供有价值的数据，遗传力量调节进化的大片段的基因组在自然种群。

Schaeffer 9726825 The research goals of this project are to test hypotheses about the genetic forces that modulate variation of chromosomal alterations that modify gene order known as inversions. The chromosomal inversions on the third chromosome of Drosophila pseudoobscura have figured prominently in the literature of evolutionary biology for more than fifty years. They have proven to be a very useful model system for studies of geographic variation, natural selection, gene flow, and genetic drift. The inversions seem to represent a clear case of adaptive selection because they vary in frequency with the environment, form classical clines, and in some populations there are seasonal cycles of inversion frequency. The objective of this proposal is to determine how selection acts on the genetic contents of inversions within and among D. pseudoobscura populations. This research will discriminate between various models of selection by analyzing nucleotide diversity of nine PCR amplified markers uniformly distributed on the third chromosome of D. pseudoobscura. The nine markers will be sequenced in D. pseudoobscura strains collected from four populations that span an inversion frequency cline. Studies of molecular evolution over the past two decades have focussed on the genetic forces that shape diversity of single genes and have not considered if selection maintains assemblages of linked genes on chromosomes. It is an open question whether the association of genes on particular chromosomes within the genome happened due to selection or accident. Inversions provide an important mechanism to maintain the association of genetic diversity distributed across long distances of chromosomes. This project will provide valuable data on the genetic forces that modulate the evolution of large segments of the genome in natural populations.