A cell copies its DNA during a specific phase of the cell cycle called S phase. This stands for "synthesis phase" and it occurs between the G1 phase (first gap) and the G2 phase (second gap).

Here's a breakdown:

* G1 Phase: The cell grows and carries out normal functions.

* S Phase: DNA replication occurs. This is where the cell's DNA is duplicated, ensuring that each daughter cell will receive a complete set of chromosomes.

* G2 Phase: The cell prepares for mitosis (cell division).

* M Phase: Mitosis occurs, where the duplicated chromosomes are separated and distributed to two daughter cells.

Therefore, the copying of DNA is a crucial step in the cell cycle, ensuring that each new cell receives a complete set of genetic information.