Among eukaryotes, replication of DNA takes place in:

Cell cycle has two main phases:

• Interphase (I-phase) is the longest and metabolically active phase which has three phases, gap-1 (${G}_{1}$), S and gap-2 (${G}_{2}$).
• Division or M-phase, where actual mitosis (or meiosis) takes place.

S phase:

1. Also called the invisible phase.
2. The DNA replication takes place at this phase of interphase.
3. The 2C DNA content of a cell becomes 4C at the end of S-phase.
4. There is no change in the ploidy level.