A cell cycle is divided into G1,S,G2 and M phases. G1 or first growth is followed by S phase or synthesis phase. DNA replication occurs in S phase and DNA amount doubles up, i.e., a cell with 2C DNA in G1 phase will now have 4C DNA. G2 phase is second growth phase where the DNA content remains the same 4C. M phase is the phase of division where DNA content either regains 2C level (mitosis) or becomes halved, i.e., 1C (in meiosis). Go phase is the phase of differentiation where the cell contains DNA in the same amount as its parent cell and does not divide further.