DNA replication occurs during the S phase (Synthesis phase) of interphase in the cell cycle.

Where DNA replication happens

  • DNA replication takes place in the S phase of interphase, not during mitosis (M phase).
  • During S phase, every chromosome is copied so that each consists of two sister chromatids, doubling the amount of DNA in the cell while chromosome number stays the same.

Quick context on the cell cycle

  • The eukaryotic cell cycle is typically divided into interphase (G1, S, G2) and the M phase (mitosis and cytokinesis).
  • G1 prepares the cell and “licenses” replication origins, S does the actual DNA synthesis, and G2 checks and prepares the cell for mitosis.

Mini takeaway

  • If you see the question “during which phase of the cell cycle does DNA replication occur?” , the correct one-word answer is: S phase.

Meta description: Learn during which phase of the cell cycle DNA replication occurs, why it happens in S phase, and how it fits into G1, S, G2, and M phases for quick exam-ready understanding.