DNA, mitochondrial

DNA, mitochondrial
Mitochondrial DNA (mtDNA) is the DNA of the mitochondrion, a structure situated in the cytoplasm of the cell rather than in the nucleus (where all the other chromosomes are located). All mtDNA is inherited from the mother. There are 2 to 10 copies of the mtDNA genome in each mitochondrion. mtDNA is a double-stranded, circular molecule. It is very small relative to the chromosomes in the nucleus and so contains only a limited number of genes. It is specialized in the information it carries and encodes a number of the subunits in the mitochondrial respiratory-chain complex that the cell needs to respire. (It also contains genes for some ribosomal RNAs and transfer RNAs). Mutations (changes) in mtDNA can cause disease. The mutations often impair the function of oxidative-phosphorylation enzymes in the respiratory chain. This is especially manifest in tissues with a high energy expenditure such as brain and muscle. Point mutations in mtDNA, for example, are associated with: NARP — which stands for Neuropathy, Ataxia and Retinitis Pigmentosa: a disease with proximal muscle weakness, wobbliness, retinal disease, seizures and developmental delay; MELAS — which stands for Mitochondrial Encephalomyopathy, Lactic Acidosis and Stroke: a disease with migraine-like attacks of headache & vomiting, hemiplegia (weakness on one side of the body), visual defect, hearing loss, exercise intolerance and weakness, loss of consciousness, seizures, mental retardation or dementia, and elevated lactic acid in blood; MERRF — which stands for Myoclonic Epilepsy and Ragged Red Fibers: a disease with epilepsy, myoclonus (shock-like contraction of muscle), cerebellar dysfunction of the cerebellar portion of the brain, hearing loss and dementia; Leber's hereditary optic atrophy — the onset in midlife (average age 30) of painless central visual loss that progresses over a period averaging 4 months, affecting both eyes affected; and Leigh's syndrome — a disease starting usually in the 1st year of life with hypotonia (floppiness), episodes of vomiting, ataxia (wobbliness), choreoathetosis (abnormal involuntary writhing movements), hyperventilation, loss of motor and verbal milestones, spasticity, hearing loss, visual loss, carbohydrate intolerance, high lactic acid, and death often within 2 years of onset. All mtDNA at fertilization comes from the oocyte. Therefore, inherited mtDNA mutations are transmitted from the mother to all offspring, male and female alike. The higher the level of mutant mtDNA in the mother's blood, the higher is the frequency of clinically affected offspring and the more severely the children tend to be affected. Each cell in the body contains different mtDNA populations. Due to presence of multiple mitochondria in cells, each cell contains several mtDNA copies. This produces tissue variation so that a mutation in mtDNA vs normal mtDNA can vary widely among tissues in an individual. There is thus a threshold effect. The percent of mutant mtDNAs must be above a certain threshold to produce clinical disease. This threshold varies from tissue to tissue because the percent of mutant mDNAs needed to cause cell dysfunction varies according to the oxidative requirements of the tissue, affecting particularly organs with a high energy needs such as brain and muscle.

Medical dictionary. 2011.

Игры ⚽ Поможем написать курсовую

Look at other dictionaries:

  • Mitochondrial DNA — Human mitochondrial DNA …   Wikipedia

  • Mitochondrial disease — Classification and external resources Micrograph showing ragged red fibres, a finding seen in mitochondrial diseases. Muscle biopsy. Gomori trichrome stain …   Wikipedia

  • DNA barcoding — is a taxonomic method that uses a short genetic marker in an organism s DNA to identify it as belonging to a particular species. It differs from molecular phylogeny in that the main goal is not to determine classification but to identify an… …   Wikipedia

  • Mitochondrial DNA (journal) — Mitochondrial DNA   Abbreviated title (ISO) MDN Discipline CellBiology/Genetics/Evolution …   Wikipedia

  • DNA barcoding — ist eine taxonomische Methode zur Artenbestimmung anhand der DNA Sequenz eines Markergens[1]. Die Abfolge der Basenpaare wird dabei analog wie der Strichcode auf Lebensmittel Verpackungen als Kennzeichen für eine bestimmte Art verwendet. Der Name …   Deutsch Wikipedia

  • Mitochondrial DNA — (mtDNA) is the DNA of the mitochondrion, a structure situated in the cytoplasm of the cell rather than in the nucleus (where all the other chromosomes are located). All mtDNA is inherited from the mother. There are 2 to 10 copies of the mtDNA… …   Medical dictionary

  • DNA Solutions — is a DNA testing company[1] created by biotechnologist Vern Muir B.Sc. in 1996, and incorporated in 1998. The company created a home paternity kit in 1997 and has since expanded its services to include DNA sample storage. Contents 1 History 2 DNA …   Wikipedia

  • Mitochondrial encephalomyopathy — Classification and external resources ICD 9 277.87 MeSH D017237 A Mitochondr …   Wikipedia

  • Mitochondrial neurogastrointestinal encephalopathy syndrome — Classification and external resources ICD 9 277.87 OMIM 603041 …   Wikipedia

  • Mitochondrial membrane transport protein — Mitochondrial membrane transport proteins are proteins which exist in the membranes of mitochondria and which serve to transport[1] molecules and other factors such as ions into or out of the organelles. Examples Examples of mitochondrial… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”