G2 phase is the third subphase of interphase in the cell cycle, which follows the successful completion of S phase, during which the cells DNA is replicated. During G2 phase, the cell grows more, makes proteins and organelles, and begins to reorganize its contents in preparation for mitosis. The cell increases in size, and centrosomes of animal cells, that were duplicated during S phase, are positioned at opposite locations in the cytoplasm. During G2 phase, it is checked if any error occurred during DNA replication and if the DNA has been completely replicated. If something went wrong during S phase, M phase does not start until the errors are repaired. The end of G2 phase occurs when a threshold level of active cyclin B1/CDK1 complex, also known as Maturation promoting factor (MPF) has been reached. The activity of this complex is tightly regulated during G2.