What is mitochondrial DNA?
Besides the cell nucleus, which holds the “classic” DNA, DNA is also found in another part of the cell (an organelle) — the mitochondrion. A mitochondrion can be likened to a “power station” inside the cell, because it produces the energy needed for every biochemical reaction. Mitochondrial DNA (which we abbreviate to mtDNA) is completely different from nuclear DNA and follows somewhat different rules. Above all, mtDNA is arranged in a circle rather than in chromosomes, which makes it more like bacterial DNA. Overall it makes up only a tiny fraction of a person's genetic information, since it contains just 37 genes, and the mitochondrion uses all of their products (proteins) for its own functioning.
The most interesting thing about mtDNA, however, is that it is inherited only from the mother. This is known as maternal inheritance: a mother passes her mtDNA on to all her children, both daughters and sons, whereas a father cannot pass his on at all. This fact is used above all in studying family trees and family ties along the maternal line, and also, for example, in studying the migration of ancestors.
Mitochondrial DNA, or mtDNA, is inherited only from the mother — this is known as maternal inheritance. A mother passes her mtDNA on to all her children, daughters and sons alike, whereas a father cannot pass his on.