Cell cycle preparation — when are cells readied for genome separation? In which phase do eukaryotic cells complete preparations (protein synthesis, organelle duplication, checkpoint control) necessary for the accurate separation of the replicated genome during mitosis?

Introduction / Context:
Accurate genome partitioning requires extensive preparation. The cell coordinates DNA damage repair, centrosome maturation, and synthesis of mitotic regulators before committing to mitosis.

Given Data / Assumptions:

• S phase completes DNA replication.
• G2 follows S and precedes M phase.
• Mitotic entry is gated by the G2/M checkpoint and cyclin B–CDK1 activation.

Concept / Approach:

During G2, cells verify DNA integrity, repair damage, accumulate mitotic cyclins, and prepare the cytoskeleton and organelles for division. Only after successful G2/M checkpoint passage do cells enter M phase to segregate chromosomes using the spindle.

Step-by-Step Solution:

Verification / Alternative check:

Inhibition of G2-specific regulators or DNA damage accumulation arrests cells prior to mitosis, confirming G2 as the preparation stage for genome separation.

Why Other Options Are Wrong:

G1 primes for DNA synthesis; S replicates DNA; M executes separation; cytokinesis (C) is after separation.

Common Pitfalls:

Confusing preparation (G2) with execution (M). The cell must clear G2/M checkpoint before mitotic spindle engagement.

Final Answer:

G2 phase