Which phase of the cell cycle is directly before mitosis?

The phase of the cell cycle that occurs directly before mitosis is the G2 phase. During this phase, the cell undergoes significant preparation for division. It involves the final growth and checks necessary for successful mitosis. The cell produces proteins and organelles, synthesizes RNA, and duplicates its centrosomes, which are crucial for the formation of the mitotic spindle during mitosis.

G2 is characterized by the completion of DNA replication, ensuring that each chromosome has been duplicated. This phase serves as a quality control checkpoint to confirm that the DNA is intact and that the cell is adequately equipped to enter mitosis. The processes that occur in G2 are essential for the cell to transition smoothly into the mitotic phase, where it divides to form two daughter cells.

In contrast, the G1 phase involves cell growth and the synthesis of proteins necessary for DNA synthesis but occurs before DNA replication. The S phase is where DNA replication actually takes place, which is crucial but not the phase immediately preceding mitosis. Interphase includes G1, S, and G2 phases; thus, while it technically encompasses G2, it is not specific to the immediate preparation for mitosis.