Nearly every eukaryote has at least two separate genomes — one in the central nucleus and one in the mitochondria — and when those two genomes act like a pair of "mismatched" partners, the "dance" they do falls apart and the results can be "disastrous," Not Exactly Rocket Science's Ed Yong says. The mitochondrial genome and the nuclear genome, though they evolved in different ways, must work together within the cell.