# DBT JRF 2020 — Question 29

Exam: DBT JRF 2020 · Section: A · Topic: Molecular Biology · Difficulty: Easy

## Question

Which of the following is/are critical for genome replication?

## Options

- **A.** all of the given options are correct
- **B.** ligase
- **C.** polymerase
- **D.** helicase

## Answer

Option A

## Explanation

DNA replication requires three classes of enzymes working in concert: (1) Helicase — unwinds the double helix by breaking hydrogen bonds between base pairs at the replication fork (e.g. DnaB in bacteria); (2) DNA Polymerase — synthesises the new strand in 5'→3' direction using each parental strand as template (requires a primer); (3) DNA Ligase — seals the nicks between Okazaki fragments on the lagging strand by forming phosphodiester bonds using NAD⁺ (bacteria) or ATP (eukaryotes) as cofactor. All three are indispensable for complete genome replication.

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