Emerging research shows that the packaging of mitochondrial DNA (mtDNA) into 
protein-DNA assemblies called nucleoids confers higher-order organization to the 
mitochondrial genome. Studies of nucleoid composition, structure and dynamics 
reveal the mitochondrial nucleoid to be tightly regulated in its genetic 
autonomy, macromolecular organization and distribution throughout the cell. Our 
recent research shows that mitochondrial nucleoids are self-contained genetic 
entities that do not exchange mtDNAs with each other frequently. This suggests 
that the genetic composition of a cell's nucleoids will be the key determinant 
of the cell's mtDNA dynamics, and provides a mechanistic basis for therapeutic 
methods to rescue dysfunction due to mutations in mtDNA.