In which phase of the cell cycle does DNA replication occur?

DNA replication occurs during the S phase of the cell cycle, which stands for "synthesis." This phase is specifically designated for the replication of DNA, ensuring that each daughter cell receives an identical set of chromosomes after cell division. During the S phase, the entire genome is duplicated to prepare for mitosis.

In the G1 phase, cells are growing and performing their normal functions, but DNA has not yet been replicated. Similarly, in the G2 phase, cells continue to grow and make preparations for mitosis, but the actual replication of DNA takes place in the S phase. The M phase, which includes mitosis and cytokinesis, is when the cell divides its replicated DNA and cytoplasm, but no replication occurs during this phase. Hence, S phase is clearly the phase of the cell cycle dedicated to DNA replication.