The 16 569 base pair's long mitochondrial genomes found in several hundred mitochondria per cell and is transmitted through the egg cell plasma of the fertilized egg. Nothing comes from the father.
This leads to the characteristic maternal inheritance. A large number of the functional mtDNA genes (which lack introns) have the energy metabolism to do.
Mutations in these can be passed on to anyone starting out with a lower energy reserve than others, while other mutations accumulate in body cells through life.
Mitochondrial disorders are characteristic degenerative diseases that show up later in life, mainly in muscle tissue of various kinds. Best known is a blindness that arose in middle adulthood.
Weaknesses of eye muscles are often caused by the increasing number of mitochondria with mutations.