Final answer:
G0 phase, often referred to as 'G zero' phase, is a stage in the cell cycle where cells are in a quiescent state and not actively preparing to divide. Some cells may temporarily enter G0 phase, while others, such as mature cardiac muscle and nerve cells, may remain in it permanently. Cells can exit G0 and re-enter G1 if they receive appropriate external signals.
Step-by-step explanation:
G0 in Interphase
G0 phase, or 'G zero' phase, is a phase within the cell cycle that is distinct from the G1 phase of interphase. G0 represents a quiescent state where the cell is not actively preparing to divide. This stage is significant for cells that have exited the regular cycle of cell division and can occur temporarily, for example, due to external factors like nutrient availability, or it can be permanent in cells such as mature cardiac muscle and nerve cells that no longer divide. When conditions are favorable or an external signal is received, some cells can leave G0 phase and re-enter G1 phase to commence preparation for cell division.