Mitochondrial DNA (mtDNA) is the DNA located in organelles called mitochondria. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known In Cell biology, an organelle (pronunciation /ɔː(rgəˡnɛl/ is a specialized subunit within a cell that has a specific function and is usually separately enclosed In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells. Most other DNA present in eukaryotic organisms is found in the cell nucleus. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex In Cell biology, the nucleus (pl nuclei; from Latin la ''nucleus'' or la ''nuculeus'' "little nut" or kernel is a membrane-enclosed 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. eVolution is the third Album by eLDee, it was due to be released in 2008 Circular DNA is a form of DNA that is found in Bacteria and Archaea as well as in eukaryotic cells in the form of Mitochondrial DNA. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Each mitochondrion is estimated to contain 2-10 mtDNA copies. ^[1] 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. Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands eVolution is the third Album by eLDee, it was due to be released in 2008 In most multicellular organisms, mtDNA is inherited from the mother (maternally inherited). Mechanisms for this include simple dilution (an egg contains 100,000 to 1,000,000 mtDNA molecules, whereas a sperm contains only 100 to 1000), degradation of sperm mtDNA in the fertilized egg, and, at least in a few organisms, failure of sperm mtDNA to enter the egg. The term sperm is derived from the Greek word (σπέρμα sperma (meaning "seed" and refers to the male reproductive cells. Whatever the mechanism, this single parent (uniparental) pattern of mtDNA inheritance is found in most animals, most plants and in fungi as well. mtDNA is particularly susceptible to reactive oxygen species generated by the respiratory chain due to its close proximity. Reactive oxygen species (ROS are ions or very small molecules that include Oxygen Ions free radicals, and Peroxides both inorganic and An electron transport chain couples a chemical reaction between an electron donor (such as NADH) and an electron acceptor (such as O2) to the transfer Though mtDNA is packaged by proteins and harbors significant DNA repair capacity, these protective functions are less robust than those operating on nuclear DNA and therefore thought to contribute to enhanced susceptibility of mtDNA to oxidative damage. Mutations in mtDNA cause maternally inherited diseases and are thought to be a major contributor to aging and age-associated pathology.

In humans (and probably in metazoans in general), 100-10,000 separate copies of mtDNA are usually present per cell (egg and sperm cells are exceptions). In mammals, each circular mtDNA molecule consists of 15,000-17,000 base pairs, which encode the same 37 genes: 13 for proteins (polypeptides), 22 for transfer RNA (tRNA) and one each for the small and large subunits of ribosomal RNA (rRNA). In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by In Molecular biology, two Nucleotides on opposite complementary DNA or RNA strands that are connected via Hydrogen bonds are called Transfer RNA (abbreviated tRNA) is a small RNA (usually about 74-95 nucleotides that transfers a specific Amino acid to a growing polypeptide chain at Ribosomal RNA ( rRNA) is the central component of the Ribosome, the protein manufacturing machinery of all living cells. This pattern is also seen among most metazoans, although in some cases one or more of the 37 genes is absent and the mtDNA size range is greater. Even greater variation in mtDNA gene content and size exists among fungi and plants, although there appears to be a core subset of genes that are present in all eukaryotes (except for the few that have no mitochondria at all). Some plant species have enormous mtDNAs (as many as 2,500,000 base pairs per mtDNA molecule) but, surprisingly, even those huge mtDNAs contain the same number and kinds of genes as related plants with much smaller mtDNAs.

Contents 1 Use in identification 2 Mitochondrial inheritance 2.1 Female inheritance 2.2 Male inheritance 3 Genes 4 Genetic influence 4.1 Genetic illness 5 See also 6 References 7 External links

Use in identification

Unlike nuclear DNA, which is inherited from both parents and in which genes are rearranged in the process of recombination, there is usually no change in mtDNA from parent to offspring. Genetic recombination is the process by which a strand of genetic material (usually DNA; but can also be RNA) is broken and then joined to a different DNA molecule Although mtDNA also recombines, it does so with copies of itself within the same mitochondrion. Because of this and because the mutation rate of animal mtDNA is higher than that of nuclear DNA,^[2] mtDNA is a powerful tool for tracking ancestry through females (matrilineage) and has been used in this role to track the ancestry of many species back hundreds of generations. Matrilineality is a system in which lineage is traced through the mother and maternal ancestors Human mtDNA can be used to identify individuals. ^[3]

Forensic laboratories occasionally use mtDNA comparison to identify human remains, and especially to identify older unidentified skeletal remains. Although unlike nuclear DNA mtDNA is not specific to one individual, it can be used in combination with other evidence (anthropological evidence, circumstantial evidence, and the like) to establish identification. mtDNA is also used to exclude possible matches between missing persons and unidentified remains. ^[4] Many researchers believe that mtDNA is better suited to identification of older skeletal remains than nuclear DNA because it is often easier to harvest from older remains because of the greater number of copies of mtDNA per cell, and because a match with a living relative is possible even if numerous maternal generations separate the two. American outlaw Jesse James's remains were identified using a comparison between mtDNA extracted from his remains and the mtDNA of the son of the female-line great-granddaughter of his sister. The United States of America —commonly referred to as the Jesse Woodson James (September 5 1847—April 3 1882 was an American Outlaw in the border state of Missouri and the most famous member of the ^[5]

Because the base sequence of animal mtDNA changes rapidly, it is useful for assessing genetic relationships of individuals or groups within a species and also for identifying and quantifying the phylogeny (evolutionary relationships; see phylogenetics) among different species, provided they are not too distantly related. To do this, biologists determine and then compare the mtDNA sequences from different individuals or species. Data from the comparisons is used to construct a network of relationships among the sequences, which provides an estimate of the relationships among the individuals or species from which the mtDNAs were taken. This approach has limits that are imposed by the rate of mtDNA sequence change. In animals, the rapid rate of change makes mtDNA most useful for comparisons of individuals within species and for comparisons of species that are closely or moderately-closely related, among which the number of sequence differences can be easily counted. As the species become more distantly related, the number of sequence differences becomes very large; changes begin to accumulate on changes until an accurate count becomes impossible.

Mitochondrial inheritance

Female inheritance

In sexually reproducing organisms, mitochondria are normally inherited exclusively from the mother. The Evolution of sexual reproduction is a major puzzle The first Fossilized evidence of sexually reproducing Organisms is from Eukaryotes of the Stenian The mitochondria in mammalian sperm are usually destroyed by the egg cell after fertilization. Also, most mitochondria are present at the base of the sperm's tail, which is used for propelling the sperm cells. Sometimes the tail is lost during fertilization. In 1999 it was reported that paternal sperm mitochondria (containing mtDNA) are marked with ubiquitin to select them for later destruction inside the embryo. Year 1999 ( MCMXCIX) was a Common year starting on Friday (link will display full 1999 Gregorian calendar) Ubiquitin is a highly-conserved regulatory Protein that is ''ubiquitously'' expressed in Eukaryotes. An embryo (from Greek:, plural, lit "that which grows" from en- "in" + bryein "to swell be full" is a multicellular ^[6] Some in vitro fertilization techniques, particularly injecting a sperm into an oocyte, may interfere with this.

The fact that mitochondrial DNA is maternally inherited enables researchers to trace maternal lineage far back in time. Matrilineality is a system in which lineage is traced through the mother and maternal ancestors (Y chromosomal DNA, paternally inherited, is used in an analogous way to trace the agnate lineage. The Y chromosome is the sex-determining Chromosome in most Mammals including Humans In mammals it contains the gene SRY, which triggers ) This is accomplished in humans by sequencing one or more of the hypervariable control regions (HVR1 or HVR2) of the mitochondrial DNA. A hypervariable region (HVR is a location within Nuclear DNA or the D-loop of Mitochondrial DNA in which Base pairs of Nucleotides HVR1 consists of about 440 base pairs. These 440 base pairs are then compared to the control regions of other individuals (either specific people or subjects in a database) to determine maternal lineage. Most often, the comparison is made to the revised. Vilà et al have published studies tracing the matrilineal descent of domestic dogs to wolves. ^[7] The concept of the Mitochondrial Eve is based on the same type of analysis, attempting to discover the origin of humanity by tracking the lineage back in time. Mitochondrial Eve ( mt-mrca) is the name given by researchers to the woman who is defined as the Matrilineal most recent common ancestor (MRCA for all currently Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus

Because mtDNA is not highly conserved and has a rapid mutation rate, it is useful for studying the evolutionary relationships - phylogeny - of organisms. Biologists can determine and then compare mtDNA sequences among different species and use the comparisons to build an evolutionary tree for the species examined.

Male inheritance

It has been reported that mitochondria can occasionally be inherited from the father in some species such as mussels. In genetics, paternal mtDNA transmission and paternal mtDNA inheritance refer to the incidence of paternal Mitochondrial DNA (mtDNA being passed on The common name mussel is used for members of several different families of Clams or Bivalve Molluscs, from both saltwater and freshwater habitats ^[8][9] Paternally inherited mitochondria have also been reported in some insects such as the fruit fly^[10] and the honeybee. ^[11]

Evidence supports rare instances of male mitochondrial inheritance in some mammals as well. Specifically, documented occurrences exist for mice,^[12][13] where the male-inherited mitochondria was subsequently rejected. It has also been found in sheep,^[14] and in cloned cattle. ^[15] It has been found in a single case in a human male and was linked to infertility. ^[16]

While many of these cases involve cloned embryos or subsequent rejection of the paternal mitochondria, others document in vivo inheritance and persistence under lab conditions.

Genes

• ATP synthase: MT-ATP6, MT-ATP8

• cytochrome c oxidase: MT-CO1, MT-CO2, MT-CO3, MT-CYB

• NADH dehydrogenase: MT-ND1, MT-ND2, MT-ND3, MT-ND4, MT-ND4L, MT-ND5, MT-ND6

• 12S, 16S: MT-RNR1, MT-RNR2

• tRNA: MT-TA, MT-TC, MT-TD, MT-TE, MT-TF, MT-TG, MT-TH, MT-TI, MT-TK, MT-TL1, MT-TL2, MT-TM, MT-TN, MT-TP, MT-TQ, MT-TR, MT-TS1, MT-TS2, MT-TT, MT-TV, MT-TW, MT-TY, MT1X

Genetic influence

Genetic illness

Mutations of mitochondrial DNA can lead to a number of illnesses including exercise intolerance and Kearns-Sayre syndrome (KSS), which causes a person to lose full function of their heart, eye, and muscle movements. An ATP synthase ( is a general term for an Enzyme that can synthesize Adenosine triphosphate (ATP from Adenosine diphosphate (ADP and inorganic The Enzyme cytochrome c oxidase or Complex IV () is a large Transmembrane protein complex found in Bacteria and the Mitochondrion NADH dehydrogenase ( is an Enzyme located in the inner mitochondrial membrane that catalyzes the transfer of Electrons from NADH to Coenzyme MT-ND1 is a mitochondrial Gene. It is associated with Mitochondrial encephalomyopathy lactic acidosis and stroke-like episodes. MT-ND5 is a mitochondrial gene It is associated with Mitochondrial encephalomyopathy lactic acidosis and stroke-like episodes. Transfer RNA (abbreviated tRNA) is a small RNA (usually about 74-95 nucleotides that transfers a specific Amino acid to a growing polypeptide chain at MT-TH is a mitochondrial gene It is associated with Mitochondrial encephalomyopathy lactic acidosis and stroke-like episodes. MT-TL1 is a mitochondrial gene It is associated with Mitochondrial encephalomyopathy lactic acidosis and stroke-like episodes. Exercise intolerance is a condition where the Patient is unable to do Physical exercise at the level or for the duration that would be expected of someone in Kearns-Sayre syndrome (abbreviated KSS) or Ragged Red Fiber Myopathy or Oculocraniosomatic Syndrome is a disease caused by a 5000 base deletion in the (See also Mitochondrial disease). Mitochondrial diseases are a group of disorders relating to the mitochondria, the Organelles that are the "powerhouses" of the eukaryotic cells

See also

• Mitochondrial disease
• Human mitochondrial genetics
• Paternal mtDNA transmission
• Single origin theory
• Mitochondrial Eve
• Mitochondrial CRS

References

External links

• Mitomap - a human mitochondrial genome database [2]
• Defining mutations of mtDNA haplogroups and subclades
• MitoSearch : public mtDNA database
• mtDNA mutation rates
• A polymorphism in mitochondrial DNA associated with IQ?
• mtDNA and the global diaspora of modern humans Professor Stephen Oppenheimer's Genetic Map
• EMPOP - Mitochondrial DNA Control Region Database

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