Organelle Genomes--Going, Going, Gone

The organelles of eukaryotic cells—chloroplasts and mitochondria—first arose as engulfed symbionts with their own genomes. They subsequently lost most of their genes to the nucleus, retaining a few that could not be transferred. In his Perspective, Palmer discusses recent evidence that suggests that another organelle, the hydrogenosome, is a highly modified mitochondrion that has lost all of its genetic material.