DNA, mitochondrial

DNA, mitochondrial The DNA of the mitochondrion, a structure situated in the cytoplasm of the cell rather than in the nucleus, where all the other chromosomes are located. Abbreviated mtDNA. mtDNA is inherited from the mother. There are 2 to 10 copies of the mtDNA genome in each mitochondrion. mtDNA is a double-stranded, circular molecule. It is very small compared to the chromosomes in the nucleus, and it contains only a limited number of genes. It is specialized in the information it carries, and it encodes a number of the subunits in the mitochondrial respiratory-chain complex that the cell needs in order to respire. Mutations (changes) in mtDNA can cause disease, and they often impair the function of oxidative-phosphorylation enzymes in the respiratory chain, especially in tissues with high energy expenditure, such as brain and muscle tissues. See also mitochondrial disease.