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

DNA replication occurs during the S phase of the cell cycle. The S phase, or synthesis phase, is specifically designated for the replication of the cell's genetic material, ensuring that each daughter cell will have an identical set of chromosomes following cell division. During this phase, the cell synthesizes a complete copy of the DNA, which is crucial for cellular functions and reproduction.

In contrast, the G1 phase, which precedes the S phase, is focused on cell growth and preparation for DNA synthesis. The G2 phase, following the S phase, is dedicated to the final preparations for mitosis, including further growth and the production of proteins necessary for cell division. The M phase encompasses the actual process of mitosis and cytokinesis, where the replicated DNA is divided into two new nuclei and the cell splits into two daughter cells. Thus, the distinct function of the S phase as the time of DNA replication is what makes it the correct answer.