Mitotic cells may be in any of four phases of the normal mitotic cycle.
Growth: G1 or G0 phase or resting phase (quiescent), preparation for chromosomal replication. This is the phase between M and S phase.
DNA replication: S (synthesis) phase. Doubling of the genome.
Growth and final preparation for division: G2 phase. This is the phase between S and M phase.
Mitosis: M phase (prophase, prometaphase, metaphase, anaphase, telophase). Halving of the genome, that has been doubled during S phase.
Facultative mitotic cells are arrested in the G0 phase, but can enter the cycle if necessary. Post-mitotic cells have left the mitotic cycle and cannot reenter it.
Following mitosis, the mitotic cells enter the G1 (gap) phase, which is of variable duration. The facultative mitotic cells enter a G0 phase, during which they perform various specialized functions. The G1 phase is followed by DNA synthetic phase (S) and a second gap (G2)