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

DNA replication occurs during interphase, which is the phase of the cell cycle that prepares a cell for division. Interphase consists of three stages: G1 (gap 1), S (synthesis), and G2 (gap 2). It is during the S phase that DNA is replicated, resulting in two identical copies of each chromosome, referred to as sister chromatids. This is a crucial step because, without DNA replication, each daughter cell would not receive the correct genetic information necessary for proper functioning.

In contrast, the other phases listed do not involve DNA replication. Prophase is part of mitosis where the chromatin condenses into visible chromosomes and the nuclear envelope begins to break down. Metaphase is also a phase of mitosis characterized by the alignment of chromosomes in the center of the cell, and telophase marks the conclusion of mitosis when the chromosomes begin to de-condense and the nuclear envelope re-forms around each set of chromosomes. Therefore, interphase is essential for ensuring that the genetic material is accurately duplicated and available for the subsequent cell division.