Mitochondrial DNA

Mitochondrial DNA (mtDNA) is the DNA located in organelles called mitochondria. Most other DNA present in eukaryotic organisms is found in the cell nucleus. Nuclear and mitochondrial DNA are thought to be of separate evolutionary origin, with the mtDNA being derived from the circular genomes of the bacteria that were engulfed by the early ancestors of today's eukaryotic cells. Each mitochondrion is estimated to contain 2-10 mtDNA copies. In the cells of extant organisms, the vast majority of the proteins present in the mitochondria (numbering approximately 1500 different types in mammals) are coded for by nuclear DNA, but the genes for some of them, if not most, are thought to have originally been of bacterial origin, having since been transferred to the eukaryotic nucleus during evolution. Among multicellular animals (metazoans), nearly all of the mtDNA in a fertilized egg (zygote) is inherited from only one parent - the female. One mechanism for this is simple dilution: an egg contains 100,000 to 1,000,000 mitochondria, whereas a sperm contains only 10 to 100. Another mechanism, documented for a few organisms, is that the sperm mitochondria do not enter the egg. Whatever the mechanism, this single parent (uniparental) pattern of mtDNA inheritance is found in most animals, most plants and in fungi as well.
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DNA deoxyribonucleic acid. complementary DNA , copy DNA. DNA transcribed from a specific RNA through the action of the enzyme reverse transcriptase. [more]Mitochondrial DNA - Community and Resources

The maternally inherited nucleic acid found in cytoplasm whose homologue in plants is chloroplastic DNA. This small circular DNA codes for tRNAs, rRNAs and some mitochondrial DNAs. It is more closely related to bacterial DNA than to eukaryotic nuclear DNA. Mitochondrial DNA mutates 10-20 times faster than nuclear DNA.