The discovery of mitochondrial DNA supports the endosymbiotic theory, which explains that an endosymbiont is a single organism that lives inside another organism. The chloroplast and the mitochondrion both represent organelles that used to be free-living cells, which ended up in host cells. Through rigorous study, scientists found that both mitochondria and plastids inside the cells of plans had their own DNA that was different from the DNA of other cells and was more similar to those from prokaryotes. Thus, this evidence supports the theory that organelles result from outside the eukaryotic cells.
Mitochondria are only inherited from the mother because, in the spermatozoa of mammals, mitochondria are destroyed by the cells of the egg after it has been fertilized. As a result, no paternal DNA can be received by the offspring. Scientists have traced mitochondrial DNA for a long time because they allow for identifying and recording the mutations that have occurred over some time, passing from one generation to another. Tracking the variations is also done on a geographic basis because certain populations will share DNA and specific mutations.
Alzheimer’s is a mitochondrial dysfunction that affects the nervous system and the rest of the body (Bell et al., 2021). The disorder slowly and steadily destroys thinking and memory skills and, subsequently, the ability to carry out simple tasks. The symptoms of the disease can occur as early as thirty years old, although it is more common to be diagnosed after sixty (National Institute on Aging, 2021). Developing through stages that differ by severity, Alzheimer’s can begin with minor issues such as memory loss and taking longer time to complete tasks, progressing into increased confusion and issues recognizing friends and family, and ending with inability to communicate, seizures, and loss of control over the body.
References
Bell, S. M., Barnes, K., De Marco, M., Shaw, P. J., Ferraiuolo, L., Blackburn, D. J., Venneri, A., & Mortiboys, H. (2021). Mitochondrial dysfunction in Alzheimer’s disease: A biomarker of the future? Biomedicines, 9(1), 63.
National Institute on Aging. (2021). What is Alzheimer’s disease?