What phase of the cell cycle involves DNA replication?

The phase of the cell cycle that involves DNA replication is the Synthesis (S) phase. During this phase, the cell synthesizes a complete copy of its DNA, ensuring that each new cell will have the same genetic material as the original cell. This process is crucial for cellular division, as it prepares the cell for mitosis by doubling the amount of genetic material.

In Gap 1 (G1), the cell grows and carries out normal metabolic processes but does not yet replicate DNA. The Gap 2 (G2) phase is where the cell continues to grow and prepares for mitosis, but it does so with the DNA that has already been replicated during the S phase. Mitosis (M) is the process of cell division itself, where the replicated DNA is separated into two new daughter cells, but it is not the phase where DNA replication occurs.

Thus, the S phase is specifically designated for the replication of DNA, making it the correct answer to the question.