We study the molecular cell biology of mitochondrial and chloroplast di. Though we know that these two organelles arose from bacteria, we know little about how they are replicated and distributed at cell di. These are basic questions of biology, and answers to them will help us understand how these respiratory and photosynthetic machines have been retained by cells for millions of years. Our model organisms are protists, such as the amoeba, Dictyostelium, and unicellular algae