Animal cells actively replicate their genetic material during the S phase of the cell cycle.

Here's a breakdown:

* Cell cycle: The cell cycle is the series of events that a cell goes through from its formation to its division. It has four main phases:

* G1 phase: The cell grows and produces proteins and organelles.

* S phase: DNA replication occurs.

* G2 phase: The cell continues to grow and prepares for mitosis.

* M phase: The cell divides into two daughter cells.

* S phase: This is the phase where the cell's DNA is duplicated. The process of DNA replication ensures that each new daughter cell will receive a complete set of chromosomes.

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