What does the term G0 refer to in cellular biology?

The term G0 refers to a resting phase of cells where they are not actively dividing. In the cell cycle, G0 is essentially a state of quiescence. Cells that enter G0 have exited the active cycle of growth and division, often due to a lack of necessary signals for division or an environmental factor that promotes stability over proliferation. In this state, cells remain metabolically active but do not progress through the stages of growth and division (like the G1, S, G2, and M phases).

Some cells may remain in G0 indefinitely, while others can re-enter the cell cycle in response to specific stimuli, allowing them to resume growth and division when conditions are favorable. This phase is critical for tissues that require long-term stability and for cells that need to maintain their function without the need for constant renewal or replication, such as neurons and muscle cells.