G0 phase

The G0 phase (G sub 0) is a period in the cell cycle where cells exist in a quiescent state. Cells enter the G0 phase from a cell cycle checkpoint in the G1 phase, such as the restriction point (animal cells) or the start point (yeast). This usually occurs in response to a lack of growth factors or nutrients. During the G0 phase, the cell cycle machinery is dismantled and cyclins and cyclin-dependent kinases disappear. Some cells remain in the G0 phase until there is a reason for them to divide.

Although many cells in the G0 phase may die along with the organism, this does not mean that cells that enter the G0 phase are destined to die; this is simply a consequence of the cell lacking any stimulation to re-enter in the cell cycle.