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

During the S phase, which stands for synthesis phase, DNA replication occurs. This is a crucial part of the cell cycle, as it ensures that each daughter cell will have an identical set of chromosomes after cell division. During the S phase, the cell synthesizes a complete copy of its DNA, preparing for mitosis. This process involves the unwinding of the DNA double helix and the pairing of complementary nucleotides to form two identical DNA strands.

In contrast, the G1 phase is primarily concerned with cell growth and preparation for DNA synthesis. The G2 phase follows S phase and involves further growth and preparation for cell division, including the synthesis of proteins necessary for mitosis. The M phase is the period of actual cell division, where the replicated DNA is separated into two new cells. Each of these phases plays a critical role in the overall process of the cell cycle, but it is specifically during the S phase that DNA replication takes place.