The GATE Grind

GATE 2025 BT – Question 50

Genetics, Cellular and Molecular Biology · Molecular Biology: Replication, transcription, splicing, translation, non-coding and micro RNA, RNA interference, DNA damage and repair · 2 marks · Multiple select

Which of the following statements about initiation of DNA replication in eukaryotes is/are true?

  1. DNA replication is initiated at the origin of replication licensed by loading of Mcm helicase complex
  2. Loading of Mcm helicase complex takes place in S phase
  3. Mcm helicase complex are activated by S-Cdks
  4. Mcm helicase complex is responsible for loading of origin recognition complex

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Correct answer: (A) DNA replication is initiated at the origin of replication licensed by loading of Mcm helicase complex; (C) Mcm helicase complex are activated by S-Cdks

Explanation

Origins are licensed in G1 when the Mcm helicase is loaded onto the origin bound by ORC (B false, and D is the wrong way round: ORC helps to load Mcm). In S phase S-Cdk (and DDK) activate the Mcm helicase and the replication starts (A and C).