What happens to the cell's DNA during the S phase?

During the S phase of the cell cycle, DNA replication occurs, which is the process of copying the cell’s DNA. This is a critical step prior to cell division, ensuring that each daughter cell will receive an exact copy of the genetic material.

During this phase, the cell synthesizes new strands of DNA alongside the existing strands, resulting in two complete sets of chromosomes. This process is essential for the growth and reproduction of cells, allowing for genetic continuity. The accurate copying of DNA is crucial because it prevents mutations and preserves the integrity of the genetic information being passed on.

While other processes such as DNA condensation into chromosomes typically occur in later phases, such as prophase of mitosis, and DNA repair processes can happen at various points during the cell cycle, the primary and defining event of the S phase is the replication or copying of DNA. Thus, the focus is on how the DNA is entirely copied to prepare for subsequent cell division.