Biology · Cell Cycle and Cell Division · NEET
S phase. This is a very common mix-up. NCERT is exact: the centriole duplicates in the cytoplasm during the S phase, at the same time DNA replicates in the nucleus. It does NOT wait for G2. In G2 the cell only makes proteins and keeps growing. So the correct answer to any NEET question asking when the centriole/centrosome duplicates is S phase, not G2.
A centriole is a small cylinder made of microtubules. A centrosome is the region of the cell that contains a pair of centrioles plus the material around them, and it acts as the main microtubule organising centre. In an animal cell there is one centrosome (with two centrioles). When we say 'the centriole duplicates in S phase', it means the centrosome becomes two, so the cell now has two centrosomes ready to go to opposite poles. For NEET, both 'centriole duplicates' and 'centrosome duplicates' are treated as happening in S phase (NEET has asked it both ways).
Movement happens later, in prophase of M phase — not in S phase. In S phase the centriole only makes a copy (duplicates). The two centrosomes then begin moving toward opposite poles of the cell during prophase, where they organise the spindle fibres. So remember two separate events: duplication = S phase, movement to poles = prophase. NEET options often mix these two to trap you.
Because both are things the cell must copy exactly once before it divides, so that each daughter cell gets one full set. DNA is copied so both daughters get complete genetic material; the centrosome is copied so both daughters get a microtubule organising centre. The cell links both copy events to the S (Synthesis) phase to keep the division balanced. This is why S phase is the single 'copying' phase of interphase.
No. Duplication is finished before M phase begins. M phase (mitosis) is when the already-duplicated chromosomes and centrosomes are separated and pulled apart, not copied. The copying of the centriole is complete in S phase during interphase. In M phase the two centrosomes simply move apart and form the spindle. So M phase = separation, S phase = duplication.
The centriole undergoes duplication during:
Given are two statements. Statement 1: During G0 phase of cell cycle, the cell is metabolically inactive. Statement 2: The centrosome undergoes duplication during S phase of interphase. Choose the most appropriate answer:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
In the S (Synthesis) phase of interphase, the same phase in which DNA replicates.
Yes. Duplicating the centriole means the centrosome becomes two, and both events occur in S phase. NEET has asked it as both 'centriole duplicates' (2021) and 'centrosome duplicates' (2023) — the answer is S phase either way.
In the cytoplasm, while DNA replicates in the nucleus. Both happen at the same time during S phase.
In prophase of mitosis, not in S phase. S phase is only for duplication; the movement and spindle formation happen later in M phase.
Interphase — specifically S phase. It is completed before M phase (mitosis) begins.
