DNA Replication: Mechanisms and Enzymes · Zoology

In eukaryotes, the 'Pre-Replication Complex' is licensed during which phase of the cell cycle?

  1. S phase, when replication begins
  2. G1 phase
  3. G2 phase, after replication is complete
  4. M phase, during chromosome segregation
Show answer and explanation

Correct answer: G1 phase

To ensure DNA is replicated only once per cycle, the Origin Recognition Complex (ORC) and licensing factors (Mcm2-7) assemble at origins during G1. This 'licensing' step is inactivated once the cell enters S phase, preventing re-replication.

Difficulty: Medium Question 18 of 20

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