Correct option is A
Explanation-
Option A - "Pre-replicative complex (Pre-RC) remains bound to the DNA in the S-phase and does not allow the re-replication"
The Pre-RC does not remain bound to DNA in S-phase. In the G1 phase, when Cdk activity is low, the Pre-RC assembles on origins of replication. At the start of S-phase, once DNA replication begins, the Pre-RC is disassembled. This disassembly ensures that DNA replication origins fire only once, preventing re-replication. Once replication starts, Cdk activity increases, and Pre-RC components (like Cdc6, Cdt1) are inactivated or degraded.
Therefore, this option is factually incorrect—it suggests the opposite of what actually happens.
Correct statements-
Option B - "Assembly of Pre-RC is inhibited by Cdk activity"
Cdks (cyclin-dependent kinases) play a central role in controlling Pre-RC assembly. When Cdk levels are high (during S, G2, M phases), Pre-RC assembly is inhibited. High Cdk activity phosphorylates and inactivates key Pre-RC components like Cdc6 and ORC proteins, blocking re-assembly. This prevents re-licensing of replication origins, hence avoiding re-replication. Only in G1 phase (when Cdk activity is low) can Pre-RC form again for the next cycle.
Option C - "Assembly of Pre-RC is initiated at the end of mitosis, at the early G1 phase of the cell cycle (when the APC activity is high)"
During late M phase and early G1, APC (Anaphase Promoting Complex) is highly active. APC promotes the degradation of cyclins, which causes a drop in Cdk activity. This low Cdk activity in G1 is a prerequisite for Pre-RC formation. Hence, the origins of replication are licensed (loaded with MCM helicase) during this window. As the cell enters S-phase, Cdk activity rises again and blocks further Pre-RC formation.
Option D - "Cdt1 that helps in the recruitment of MCM proteins in the G1 phase is inactivated by geminin in the S-phase of the cell cycle"
Cdt1 is a licensing factor that loads MCM helicase onto DNA during G1 phase. In higher eukaryotes, geminin binds to Cdt1 and inhibits it during S-phase to prevent re-licensing. Although budding yeast (S. cerevisiae) doesn't use geminin, the same logic applies—Cdt1 is tightly regulated (e.g., via degradation or export). This ensures that DNA replication does not restart at the same origins in the same cycle.
Since option A is the only incorrect statement among all the other options that makes it a correct answer.
