DISSERTATION RESEARCH: Polymorphism, Divergence, and Selection in Sex-specific Mitochondrial DNA in the Mussel, Mytilus

线粒体是负责将食物中的能量转化为细胞可使用的分子货币的细胞器。它们通常是母系遗传的，并拥有自己的小基因组。在过去的十年里，关于自然选择在影响线粒体DNA(MtDNA)进化中的重要性一直存在相当大的争论。证据表明，选择可以解释在物种间线粒体DNA序列比较中发现的一些频率和突变类型的差异。然而，这一证据常常被被比较物种的人口历史差异所混淆，即稳定的种群表现出不同于增长或收缩的种群的模式。我们的研究利用了贻贝科贻贝mtDNA的一种不寻常的遗传模式，在这种模式下，两个线粒体基因组同时存在，一个是母系遗传的，另一个是父系遗传的。由于这两个基因组都有相同的人口学历史，在我们的研究中发现的两个mtDNA基因组之间的差异应该会提供一个更清晰的选择信号。理解选择在mtDNA中的作用对于理解人类线粒体疾病和其他基于遗传的疾病是重要的。此外，线粒体DNA经常被用作确定动植物种群结构的工具，这在确定适当的保护单位方面可能是重要的。

Mitochondria are cellular organelles responsible for converting energy from food into a molecular currency useable by the cell. They are usually inherited maternally and possess their own small genome. Over the past decade, there has been considerable debate over the importance of natural selection in influencing the evolution of mitochondrial DNA (mtDNA). Evidence suggests that selection can explain some of the differences in frequencies and kinds of mutations found in comparisons of mtDNA sequences among species. However, this evidence is often confounded by differences in the demographic histories of the species being compared, i.e., stable populations show a different pattern than growing or contracting populations. Our study takes advantage of an unusual pattern of mtDNA inheritance in mussels of family Mytilidae in which two mitochondrial genomes exist simultaneously, one inherited maternally and the other paternally. Since both genomes share a demographic history, differences found between the two mtDNA genomes in our study should provide a much clearer signal of selection.Understanding the role of selection in mtDNA is important in understanding human mitochondrial diseases and other genetically based ailments. In addition, mtDNA is often used as a tool to identify population structure in animals and plants that can be important in identifying appropriate units for conservation.