In eukaryotes, the replication of DNA takes place at which phase of cell cycle?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → S-Phase
The cell cycle has interphase (G1, S, G2) and the M phase. DNA is copied only once in each cycle, in the S (synthesis) phase, so that each daughter cell gets a full set.
Option (1) M-Phase — Incorrect. In M phase the already-copied chromosomes are separated into two daughter cells.
Option (2) S-Phase — Correct. In eukaryotes, DNA replication takes place in the S-phase (synthesis phase) of the cell cycle. A failure in cell division after replication results in polyploidy.
Option (3) \( G_0 \) Phase — Incorrect. G0 is a resting stage where cells have left the cycle.
Option (4) \( G_1 \) Phase — Incorrect. In G1 the cell grows and prepares for DNA replication, which comes next, in S phase.
Note: A similar question was also asked in CUET (UG) 2026 on 19-05-2026 (Slot 2), and in CUET (UG) 2024 on 29-05-2024 (Slot 1).
NCERT Extract:
The Machinery and the Enzymes – “… The vectors provide the origin of replication. Further, not every detail of replication is understood well. In eukaryotes, the replication of DNA takes place at S-phase of the cell-cycle. The replication of DNA and cell division cycle should be highly coordinated.”