Mitochondrial DNA Copies

Mitochondria play the dual role of are the main intracellular source of energy and primary target of reactive oxygen species (ROS), which are generated as natural byproducts of aerobic metabolism in animal and human cells. Within each human or animal cell, there are from several hundred to over a thousand mitochondria, each containing about 2^10 copies of mitochondrial DNA (mtDNA). The number of mtDNA copies (mtDNAcn) positively correlates with the quantity and size of mitochondria.

It is essential to note that, unlike nuclear DNA, mtDNA lacks robust protective histones and possesses limited DNA repair capacity, making it particularly vulnerable to damage induced by ROS. Cells under ROS stress from ROS have been observed to increase the number of copies of their mtDNA and enhance mitochondrial abundance; this might occur as a compensatory response to mitigate damage and meet the high respiratory demands necessary for ROS detoxification from ROS.

Conversely, the expanded mitochondrial population itself generates ROS, thereby contributing to further oxidative damage to mitochondria and other intracellular constituents, including DNA, RNA, proteins, and lipids.

References

1. Han, D., E. Williams, and E. Cadenas, Mitochondrial respiratory chain-dependent generation of superoxide anion and its release into the intermembrane space. Biochem J, 2001. 353(Pt 2): p. 411-6.
2. Cavelier, L., A. Johannisson, and U. Gyllensten, Analysis of mtDNA copy number and composition of single mitochondrial particles using flow cytometry and PCR. Exp Cell Res, 2000. 259(1): p. 79-85.
3. Lee, H.C. and Y.H. Wei, Mitochondrial role in life and death of the cell. J Biomed Sci, 2000. 7(1): p. 2-15.