Extrachromosomal DNA Extrachromosomal DNA Extrachromosomal DNA is any DNA that is found outside the nucleus of a cell. It is also referred to as extranuclear DNA or cytoplasmic DNA. Most DNA in an individual genome is found in chromosomes but DNA found outside the nucleus also serves important biological functions. In prokaryotes, nonviral extrachromosomal DNA is primarily found in plasmids whereas in eukaryotes extrachromosomal DNA is primarily found in organelles. Mitochondrial DNA is a main source of this extrachromosomal DNA in eukaryotes. The fact that this organelle contains its own DNA supports the hypothesis that mitochondria originated as bacterial cells engulfed by
Complementary DNA make viral proteins to take over the host cell. An example of this first step from viral DNA to cDNA can be seen in the HIV cycle of infection. Here, the host cell membrane becomes attached to the virus’ lipid envelope which allows the viral capsid with two copies of viral genome RNA to enter the host. The cDNA copy is then made though reverse transcription of the viral RNA, a process facilitated by the chaperone CypA and a viral capsid associated reverse transcriptase. Complementary DNA In genetics, complementary DNA (cDNA) is DNA synthesized from a single-stranded RNA (e.g., messenger