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" phase. This phase is specifically dedicated to the synthesis of DNA, where the cell duplicates its genetic material to ensure that each daughter cell receives an identical copy of the DNA during cell division.

During the S phase, each chromosome is replicated to form two sister chromatids. This process is crucial for maintaining genetic continuity and stability when cells divide. The appropriate timing and regulation of DNA replication are vital for preventing errors that could lead to mutations or cancer.

In contrast, the G1 phase occurs before DNA synthesis and involves cell growth and preparation for DNA replication. The G2 phase follows the S phase and is focused on further growth and the preparation for mitosis, including the synthesis of proteins and the production of organelles. The M phase comprises the actual process of cell division itself, including mitosis and cytokinesis. Therefore, the only phase where DNA replication specifically takes place is the S phase.