The cell cycle G 0 = resting phase (nonproliferation of cells); G 1 = variable pre-DNA synthetic phase (12 h to a few days); S = DNA synthesis (usually 2 to 4 h); G 2 = post-DNA synthesis (2 to 4 h) —a tetraploid quantity of DNA is found within cells; M 1 = mitosis (1 to 2 h).