The mitochondrion, sometimes called “power-house” of the cell, mainly functions to convert food into energy through cellular respiration.  However, did you know that mitochondria have important implications for genetics as well?
In fact, the mitochondria have their own DNA.   There is evidence showing that mitochondria used to be a separate, symbiotic organism.  Mitochondrial DNA (mtDNA), which makes up less than .001% of our total DNA, is passed on only from mother to child; the mitochondria in the sperm doe not enter the egg, and the paternal mitochondria are destroyed after fertilization.  This means that all of our mtDNA comes from our mother. Since it follows the direct matrilineal line, mtDNA does not get altered by genetic exchanges (unlike nuclear DNA); the only changes in mtDNA are from natural mutations.  Because of this fact, mitochondrial DNA is extremely valuable for tracing back ancestors through the matrilineal lineage (see Mitochondrial Eve ).