Mitochondrial DNA 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 the human genome to be sequenced. In
Extrachromosomal DNA virus. Some viruses, such as HIV and oncogenetic viruses, incorporate their own DNA into the genome of the host cell. Viral genomes can be made up of single stranded DNA (ssDNA), double stranded DNA (dsDNA) and can be found in both linear and circular form. One example of infection of a virus constituting as extrachromosomal DNA is the human papillomavirus (HPV). The HPV DNA genome undergoes three distinct stages of replication: establishment, maintenance and amplification. HPV infects epithelial cells in the anogenital tract and oral cavity. Normally, HPV is detected and cleared by the immune system. The recognition of viral