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

线粒体是细胞器，负责将食物中的能量转化为细胞可用的分子货币。 它们通常是母系遗传的，拥有自己的小基因组。 在过去的十年中，有相当多的辩论在影响线粒体DNA（mtDNA）进化的自然选择的重要性。 有证据表明，选择可以解释物种间mtDNA序列比较中发现的突变频率和种类的差异。 然而，这一证据往往被所比较的物种的人口统计学历史的差异所混淆，即，稳定的种群显示出与增长或收缩种群不同的模式。 我们的研究利用了贻贝科贻贝中一种不寻常的线粒体DNA遗传模式，其中两个线粒体基因组同时存在，一个是母系遗传，另一个是父系遗传。 由于这两个基因组有着共同的人口统计学历史，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遗传性疾病非常重要。此外，线粒体DNA通常被用作鉴定动植物种群结构的工具，这对于确定适当的保护单位非常重要。

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.