DNA synthesis occurs during the S phase in the eukaryotic cell cycle (“S” phase stands for synthesis). During this phase, the cell synthesizes a complete copy of the DNA in its nucleus. The S phase follows the G1 phase and precedes the G2 phase in the interphase of the cell cycle. By completing DNA synthesis during the S phase, the cell ensures each daughter cell receives a full set of genetic information. In eukaryotes, the pace of replication is approximately 40 nucleotides per second, which is slow compared to prokaryotes such as e. Coli, which replicates 1000 nucleotides per second.