What is a characteristic of the G0 phase of the cell cycle?

The G0 phase of the cell cycle is characterized by a state in which cells are not actively preparing to divide. Instead, during this phase, cells enter a quiescent state, which means they remain metabolically active but do not progress through the cell cycle. This phase can be thought of as a resting state where the cell has exited the cycle and is temporarily inactive or has differentiated into a non-dividing cell.

Many cells enter the G0 phase in response to various environmental signals, such as nutrient availability or damage repair needs. This dormancy can be a reversible state, allowing cells to re-enter the cell cycle when conditions become favorable again.

In contrast, the options regarding cells preparing for division, growing and replicating DNA, or undergoing apoptosis pertain to different phases of the cell cycle. The preparation for division happens primarily in the G1, S, and G2 phases, while apoptosis refers to programmed cell death, which is not a characteristic of the G0 phase. Therefore, the defining feature of the G0 phase is that it is a period of dormancy or a quiet state for the cell.