When combining genetic material forming a descendant, extrachromosomal DNA located in the parents mitochondria are not combined. The sperm's mittochondria do not enter the egg cell and if ever one gets through, it's eradicated. Therefore only the mother's extrachromosomal DNA is passed to the next generation.
Figures were producedusing Servier Medical Art at www.servier.com
Examining the mitochondrial DNA and reconstructing the phylogenetic tree, leads us to what is called the "Mitochondrial Eve"