1. Mitochondria have their own DNA and are inherited only from the mother 2. Mitochondria are distr ibuted randomly in daughter cells, so these may contain normal mitochondrial dna. mutant dna or a mixture of both there is, therefore, variable expression of disease due to mutation in mitochondrial DNA, depending upon the relative proportion of normal to mutant DNA. No affected male will transmit the disease(. g. Leber's optic atrophy) 3. Mutations in mitochondrial dna occur more frequently(as much as tenfold faster ) than those in nuclear genes involved in oxidative phosphorylation 4.The physiologic effect of defective mitochondrial function depends on the energy requirements ofthe cell 5. Oxidative phosphory lation integrity declines with aging, paralleling the accumulation of mitochondrial dna mutations in somatic cell 6.The same clinical profile may result from different genetic defects, and less commonly, an identical genetic defect can result in different p 多质性 人体不同类型的细胞含线粒体数目不同,通常有成百上千个,而 每个线粒体中有2~10个 mtDNA分子,由于线粒体的大量中性突变 因此,绝大多数细胞中有多种 mtdNA拷贝,其拷贝数存在器官组织 的差异性。 细胞融合实验表明不同线粒体之间tRNA和rRNA存在翻译互补 作用,其机制可能是线粒体互相融合及 mtDNA及其转录物的再分布 、异质性9 1.Mitochondria have their own DNA and are inherited only from the mother. 2.Mitochondria are distributed randomly in daughter cells, so these may contain normal mitochondrial DNA, mutant DNA, or a mixture of both. there is, therefore, variable expression of disease due to mutation in mitochondrial DNA, depending upon the relative proportion of normal to mutant DNA. No affected male will transmit the disease (e.g. Leber’s optic atrophy). 3.Mutations in mitochondrial DNA occur more frequently (as much as tenfold faster)than those in nuclear genes involved in oxidative phosphorylation. 4.The physiologic effect of defective mitochondrial function depends on the energy requirements of the cell. 5.Oxidative phosphorylation integrity declines with aging, paralleling the accumulation of mitochondrial DNA mutations in somatic cell. 6.The same clinical profile may result from different genetic defects, and, less commonly, an identical genetic defect can result in different phenotype. 二、多质性 人体不同类型的细胞含线粒体数目不同，通常有成百上千个，而 每个线粒体中有 2～10 个 mtDNA 分子，由于线粒体的大量中性突变， 因此，绝大多数细胞中有多种 mtDNA 拷贝，其拷贝数存在器官组织 的差异性。 细胞融合实验表明不同线粒体之间 tRNA 和 rRNA 存在翻译互补 作用，其机制可能是线粒体互相融合及 mtDNA 及其转录物的再分布。 三、异质性