Mitochondrial DNA (mtDNA) dysfunction results in a broad range of human disorders. Alterations in the mitochondrial DNA give rise to a variety of neuromuscular symptoms and accumulate in inherited mitochondrial disorders, but also in the affected tissues of Parkinsons's disease patients. In spite of their medical relevance, little is known about the mechanisms by which mtDNA mutations/deletions form, which hampers the development of treatments. We investigate mtDNA maintenance in order to better understand the underlying causes of such disease states. The research consists of in vitro biochemical experiments in combination with cell biological approaches to verify any in vivo relevance.