Here's why:
* S phase (Synthesis): The S phase is the period when DNA replication occurs. This is crucial because each daughter cell needs a complete set of genetic material. Along with DNA replication, the cell also duplicates its organelles, ensuring each daughter cell receives a full complement of these essential structures.
* G1 phase (Gap 1): The G1 phase is the period of growth and preparation for DNA replication. The cell increases in size and synthesizes proteins and enzymes needed for S phase. While some organelle growth may occur, major duplication usually happens during S phase.
* G2 phase (Gap 2): The G2 phase is a period of continued growth and final preparation for cell division. Organelle duplication is essentially completed by this phase.
Important Note: Organelle duplication is a complex process and not all organelles duplicate at the same rate. For example, mitochondria and chloroplasts (in plants) replicate independently, but are influenced by the cell cycle.
