But if the mitochondria are me, doesn’t this mean I have two sets of genes? Aren’t I a mosaic of both my own cellular DNA and that of my mitochondria? The fact is that all of the “others”—whether they are parasitic or mutualistic, cheaters or straight-shooters, long-term residents or one-night stands—have a significant characteristic in common: They each carry their own DNA. And this means that, for however long they are inside their host’s body, two genetically distinct organisms are living under the same skin and, to one extent or another, are biologically intertwined. Deep down, at the core of our tissue, we are a gigantic, symbiotic array, a ragtag assortment of organisms. All of these are to some degree us.
http://nautil.us/issue/35/boundaries/parasites-are-us