"I became aware that other genetic systems with different inheritance patterns exist. From the beginning, I was curious about these unruly genes that weren't in the nucleus. The most famous of them was a cytoplasmic gene called "killer," which, in the protist Paramecium aurelia, followed certain rules of inheritance. The killer gene, after twenty years of intense work and shifting paradigmatic ideas, turns out to be in a virus inside a symbiotic bacterium. Nearly all extranuclear genes are derived from bacteria or other sorts of microbes. In the search for what genes outside the nucleus really are, I became more and more aware that they're cohabiting entities, live beings. Live small cells reside inside the larger cells." 3rd culture.