How is replication initiated differently in eukaryotes?

How is replication initiated differently in eukaryotes?

• A. Eukaryotes use a single origin per chromosome; replication begins in G1.
• B. Eukaryotic replication uses multiple origins licensed by ORC and licensing factors; replication starts in S phase and proceeds bidirectionally from many origins with telomere maintenance.
• C. Eukaryotes do not require RNA primers for replication.
• D. Eukaryotic replication relies on RNA polymerase to begin synthesis.

Answer: (B)

Replication initiation in eukaryotes relies on multiple origins across each chromosome, not a single starting point. These origins are licensed in G1 by the origin recognition complex binding and by licensing factors such as Cdc6 and Cdt1, which load the MCM helicase onto DNA. Then, when S phase begins, cell-cycle kinases activate those licensed origins and replication forks fire, allowing bidirectional replication from many origins. This setup lets the entire genome be copied efficiently within S phase and coordinates with maintaining chromosome ends through telomere maintenance. This differs from ideas of a lone origin or replication starting in G1, and it incorporates the necessity of primers and DNA polymerases rather than RNA polymerase alone to start DNA synthesis.

Replication initiation in eukaryotes relies on multiple origins across each chromosome, not a single starting point. These origins are licensed in G1 by the origin recognition complex binding and by licensing factors such as Cdc6 and Cdt1, which load the MCM helicase onto DNA. Then, when S phase begins, cell-cycle kinases activate those licensed origins and replication forks fire, allowing bidirectional replication from many origins. This setup lets the entire genome be copied efficiently within S phase and coordinates with maintaining chromosome ends through telomere maintenance. This differs from ideas of a lone origin or replication starting in G1, and it incorporates the necessity of primers and DNA polymerases rather than RNA polymerase alone to start DNA synthesis.