Molecular Biology


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                Mitochondria produce energy for your cells. They are believed to have originated from a symbiotic relationship between bacteria and cells a very long time ago. Eventually the bacteria became part of the cell, specifically the mitochondria. This explains why mitochondria have their own set of DNA instructions. Mitochondrial genomes are passed to children via the mother, which allows tracing up the female side of an ancestry, which was previously impossible.

                Mitochondrial DNA is a circular structure of DNA held within the mitochondria. A number of diseases, including Leigh syndrome, NARP, and LHON can be traced to the origin of mutated mitochondrial DNA. Since Mitochondrial DNA is circular, like that of a bacterium, it is very likely that the previously mentioned theory about mitochondrion origins lying in ancient bacteria-cell symbiosis is true.

Mitochondrial DNA was discovered by Margit M. K. and Sylvan Nass in the 1960s.

                Mitochondrial DNA encodes a few different things necessary to the human body. The “electron transport chain” is made up of the 13 protein-encoding genes. The mitochondrial genome also has 2 ribosomal RNA-encoding genes and 22 transfer RNA-encoding genes.

This type of DNA is important to evolutionary research as well. It was used to identify “Mitochondrial Eve” (the earliest female ancestor of all humans), and, with Y chromosome lineage also “mapped”, was a crucial part is proving that human ancestry meets at one point, not necessarily traced up to two humans, but traced up to two creatures at some point.


-Mitochondrial DNA is often shortened to “mtDNA”

-Ribosomal RNA is often shortened to “rRNA”

-Transport RNA is often shortened to “tRNA”

-The use of “rRNA” in the body is speculated

-“tRNA” is used to encode proteins along with messenger RNA (mRNA), which is provided by the protein-encoding genes mentioned above

-Mitochondrial DNA is transferred from mother to child in MOST cases. For some species of mussels, fruit flies, honeybees, and cicadas.

-mtDNA is inherited from the mother because a female egg holds more mtDNA information than a sperm cell, sperm mtDNA degrades once in the egg, and/or the sperm’s mtDNA does not enter the egg.

-Injecting sperm into an oocyte may interfere with the mtDNA-destroying process that usually takes place in fertilization.

-Sperm cells’ mtDNA was found to be marked with ubiquitin, which would mark it for destruction in the ovaries, in 1999.

-Very rarely, male mtDNA can be passed from father to child in mammals. This has been reported in mice, sheep, cattle, and once in a human.

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