Paper 1 Q16 — What happens in S phase

Cell cycle — DNA and centriole replication both occur in S phase (interphase)

What the examiners said

“A significant proportion of candidates selected option B, an incorrect option. These candidates did not appear to know what happens to centrioles during the S phase of the mitotic cell cycle.”

Try the question (reconstruction)

During which stage of the cell cycle are the centrioles duplicated, alongside DNA replication?

Examiner report: “Candidates did not know that centrioles are duplicated during S phase.”

Explore — walk the cell cycle

Step through the phases. Watch DNA content and centriole number — both double in S phase, well before mitosis.

Phase: G1

Interphase (G1–S–G2) is the busy preparation stage: S phase copies both the DNA and the centrioles.

Original reconstruction inspired by the misconceptions described in the Singapore-Cambridge GCE A-Level H2 Biology 9744 November 2023 Examiner Report. Not the actual examination question. For classroom exploration.

Made by lookang, using Claude Fable 5. More resources: iwant2study.org