Cell Biology:// Heteroplasmy vs. Homoplasmy

1. 출처: 마이애미 의과대학, http://hihg.med.miami.edu/code/http/modules/education/Design/CoursePageContent.asp?ID=20

- A cell can have some mitochondria that have a mutation in the mtDNA and some that do not. This is termed heteroplasmy. The proportion of mutant mtDNA molecules determines both the penetrance and severity of expression of some diseases.

- Homoplasmy refers to a cell that has a uniform collection of mtDNA: either completely normal mtDNA or completely mutant mtDNA.

- A unique feature of mtDNA is that, at cell division, the mtDNA replicates and sorts randomly among mitochondria. In turn, the mitochondria sort randomly among daughter cells. Therefore, in cells where heteroplasmy is present, each daughter cell may receive different proportions of mitochondria carrying normal and mutant mtDNA.

2. 출처: Mitochondrial DNA, https://en.wikipedia.org/wiki/Mitochondrial_DNA

Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, adenosine triphosphate (ATP). Mitochondrial DNA is only a small portion of the DNA in a eukaryotic cell; most of DNA can be found in the cell nucleus and, in plants and algae, also in [plastids] such as [chloroplasts].

In humans, the 16,569 base pairs of mitochondrial DNA encode for only 37 genes. Human mitochondrial DNA was the first significant part of the human genome to be sequenced. In most species, including humans, mtDNA is inherited solely from the mother.

Since animal mtDNA evolves faster than nuclear genetic markers, it represents a mainstay of phylogenetics and evolutionary biology. It also permits an examination of the relatedness of populations, and so has become important in anthropology and biogeography. ( ... ... )


출처 3: FAQs: Mitochondrial DNA Explained (Phillips DNA Project)


Mitochondrial DNA (mtDNA) is genetic material found in mitochondria.  It is passed down from mothers to both sons and daughters, but sons cannot pass along their mothers' mtDNA to their children.  This is because mtDNA is transmitted through the female egg.  The mtDNA found in the egg is nonrecombinant, meaning that it does not combine with any other DNA so that it is passed down virtually unchanged through the direct maternal line over the generations.  You inherited your mtDNA exclusively from your mother.

The mtDNA test is more of an anthropological test than a genealogical test.  From a genealogical standpoint, mtDNA is not very useful for two reasons.  The first reason is ( ... ... )

The second reason mtDNA is not very useful for historical genealogical research is because mtDNA mutates very, very slowly - much slower than yDNA.  This means that your mtDNA is nearly identical to the mtDNA of your straight line maternal ancestor who lived thousands of years ago, and it is also identical to thousands of people living today.  My mother has over 1,000 low resolution mtDNA matches in the FTDNA database.  This means she shares a common maternal ancestor with them somewhere back in time.  The problem is there is no way to know whether this common maternal ancestor lived recently or thousands of years ago. ( ... ... )