Homoplasmy
Homoplasmy is a term used in
The term may also refer to uniformity of plant plastid DNA, whether occurring naturally or otherwise.[citation needed]
Inheritance
In almost every species, mitochondrial DNA is maternally inherited.[2] This means that all of the offspring of a female will have identical and homoplasmic mitochondrial DNA. It is very rare for females to pass on heteroplasmic or homoplasmic mutations because of the genetic bottleneck, where only a few out of many mitochondria actually are passed on to offspring.[2]
The mussel
Mutations
There is evidence of both homoplasmic and heteroplasmic inherited mutations that lead to disease, though heteroplasmic mutations typically are a precursor to homoplasmic disease.[6][7] Many diseases resulting from mutations in mitochondrial DNA are not inherited but developed as the untranslated region of mitochondrial DNA (mtDNA) is thought to be particularly susceptible to mutation.[8] Many cancer types are the result of mutations in the mtDNA. For example, a specific type of mutation in one specific area of mtDNA was found to be in several different tumor types.[9]
Mitochondria often undergo fission and fusion, which means that different organelles in the same cell can fuse together to become one mitochondria, or can break apart and become two.[10] This process can be used to mitigate the effects of heteroplasmic mutations. Each mitochondria has multiple nucleoids, which consist of several copies of mtDNA, and when mitochondria fuse together, these nucleoids do not exchange DNA; therefore, if two mitochondria that have different DNA fuse together, they will have only two types of nucleoids. This means that fusion can be used to generate complementary nucleoids if a mutation causes one mitochondria to no longer be functional. Additionally, fission can cause one mitochondria with two different nucleoids to become two mitochondria each with only one type of nucleoid.[10] Some researchers believe that this could be a useful tool to treat diseases caused by mutations in mtDNA.[10]
Inherited homoplasmic diseases
Leber's hereditary optic neuropathy
Cancer
Some research has shown that an inherited heteroplasmic mutation can cause cancer in older age as cells become homoplasmic.[6] In one study, doctors found that a cancer patient's tumor consisted of only homoplasmic cells with mutant mtDNA and that healthy cells in his body were heteroplasmic for mutant mtDNA.[6] Additionally, researchers found that the patient's siblings had the same heteroplasmic mutation. This indicates that the heteroplasmic mutation was inherited, and over time led to homoplasmic cells that caused cancer.[6]
See also
- Heteroplasmy
- Microheteroplasmy
Notes and references
- ^ a b Heteroplasmy vs. Homoplasmy. University of Miami Faculty of Medicine. Accessed 21 October 2012.
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