Evolutionary Dynamics of Mitochondrial DNA

9707676兰德研究计划的目标是了解作用于线粒体DNA（mtDNA）变异的进化力量。 mtDNA是种群和进化生物学中最广泛使用的遗传标记，通常认为mtDNA序列的变异是中性的，即，不会被自然选择改变。然而，最近的一些报道表明，mtDNA进化偏离了各种中性模型。 虽然非中性的mtDNA进化可能会损害进化研究的特定案例，但偏离中性进化提供了机会来研究可以作用于mtDNA本身以及核质相互作用的各种一般进化力。 研究人员正在研究的主要问题是：自然选择对核性染色体和母系遗传的细胞质基因（如线粒体DNA）之间的相互作用的作用是否与常染色体和线粒体DNA之间的相互作用不同（常染色体是双亲遗传的非性染色体）。细胞核群体遗传学的理论模型表明，细胞质染色体和常染色体上的选择不能保持遗传变异。一个新的模型表明，对mtDNA和性染色体组合的选择可以保持变异。 将用来自不同生境的自然种群的大样本果蝇（Drosophila melanogaster）对该模型进行测试。 将使用分布在性别长度上的标记对个体果蝇进行多标记DNA分析（即，X染色体）和常染色体（即，第二和第三染色体）。将收集额外的DNA序列数据，以测试其他自然选择模型对mtDNA中轻度有害突变的影响。 这些研究将提供有关染色体遗传和有效种群大小如何影响进化变化的基本数据，并可能导致对染色体共同进化的一般原理有更深入的了解。

9707676 Rand The goal of the research program is to understand the evolutionary forces acting on variation in mitochondrial DNA (mtDNA). MtDNA is the most widely used genetic marker in population and evolutionary biology and it is generally assumed that the variation in mtDNA sequence is neutral, i.e., is not altered by natural selection. However, a number of recent reports have shown that mtDNA evolution departs from various neutral models. While non-neutral mtDNA evolution can compromise specific cases of evolutionary study, departures from neutral evolution offer opportunities to examine the variety of general evolutionary forces that can act on mtDNA itself, and on nuclear-cytoplasmic interactions. The main question the investigator is studying is: Does natural selection operate differently on interactions between nuclear sex chromosomes and maternally inherited cytoplasmic genes (such as mitochondrial DNA) than on interactions between autosomes and mitochondrial DNA (where an autosome is a biparentally inherited non-sex chromosome). Theoretical models of cytonuclear population genetics show that selection on cytoplasmic chromosomes and autosomes cannot preserve genetic variation. A new model shows that selection on combinations of mtDNAs and sex chromosomes can preserve variation. This model will be tested with large samples of fruit flies (Drosophila melanogaster) from natural populations in distinct habitats. Multiple-marker DNA analysis will be performed on individual fruit flies using markers spread across the length of the sex (i.e., X-chromosome) and autosomes (i.e., the 2nd and 3rd chromosomes). Additional DNA sequence data will be collected to test other models of natural selection on mildly deleterious mutations in mtDNA. These studies will provide basic data bearing on how chromosomal inheritance and effective population size affects evolutionary change, and may lead to a greater understanding of the general principles of chromosomal coevolution.