Mitochondrial DNA together with the assessment of their pathogenicity. Mitochondrial DNA Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, adenosine triphosphate (ATP). Mitochondrial DNA is only a small portion of the DNA in a eukaryotic cell; most of the DNA can be found in the cell nucleus and, in plants and algae, also in plastids such as chloroplasts. In humans, the 16,569 base pairs of mitochondrial DNA encode for only 37 genes. Human mitochondrial DNA was the first significant part of
DNA methylation in cancer and predisposes the cell and its descendants to progression to cancer. Another review also indicated an early role for hypermethylation of DNA repair genes in cancer. If a gene necessary for DNA repair is hypermethylated, resulting in deficient DNA repair, DNA damages will accumulate. Increased DNA damage tends to cause increased errors during DNA synthesis, leading to mutations that can give rise to cancer. If hypermethylation of a DNA repair gene is an early step in carcinogenesis, then it may also occur in the normal-appearing tissues surrounding the cancer from which the cancer arose (the field defect). See the table