Answer: S phase (DNA replication).
- A Prophase, prior to S phase
- B S phase (DNA replication)
- C Metaphase, before anaphase
- D G<sub>1</sub> phase, before S phase
Correct answer: B. S phase (DNA replication)
Explanation: Cohesin rings are loaded onto chromosomes and establish sister chromatid cohesion during DNA replication in S phase.
The cell cycle: G1 (growth and preparation), S (DNA replication, chromosome number stays 2n but DNA content doubles), G2 (final checks before division), and M (mitosis itself) - together, G1+S+G2 make up interphase.
Concept context
Mitosis and meiosis: how cells divide for growth, repair, and reproduction.