10. In E. coli, the major DNA unwinding protein helicase, DnaB translocate in
(1) 5’à3′ direction along the lagging strand template.
(2) 3’à5 ‘direction along the lagging strand template.
(3) 5’à3′ direction along the leading strand template.
(4) 3’à5’ direction along the leading strand template.
Introduction
In Escherichia coli, DNA replication requires the coordinated action of multiple enzymes, including the replicative helicase DnaB. This hexameric helicase unwinds double-stranded DNA ahead of the replication fork, enabling DNA polymerases to synthesize new strands. Understanding the directionality of DnaB translocation along DNA is crucial for grasping the molecular mechanics of bacterial replication. This article explains that DnaB translocates in the 5′ to 3′ direction along the lagging strand template, based on structural and biochemical evidence.
Key Findings on DnaB Helicase Directionality
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DnaB is a hexameric ring-shaped helicase that encircles single-stranded DNA (ssDNA).
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It hydrolyzes ATP to translocate along ssDNA, unwinding the double helix in its path.
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Multiple studies confirm that DnaB moves 5′ to 3′ along the single-stranded lagging strand template during replication.
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This orientation places DnaB on the lagging strand at the replication fork, unwinding DNA ahead of the replication machinery.
Supporting Evidence
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Biochemical assays demonstrate that DnaB requires a 5′ single-stranded tail to load and translocate effectively.
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Electron microscopy and structural studies reveal a central channel through which the lagging strand passes.
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DnaB’s translocation facilitates the synthesis of RNA primers by primase on the lagging strand.
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DnaB’s activity is stimulated by single-stranded DNA-binding proteins (SSB) and primase, coordinating lagging strand synthesis.
Why This Direction Matters
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The leading strand is synthesized continuously in the 5′ to 3′ direction, while the lagging strand is synthesized discontinuously as Okazaki fragments.
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DnaB’s 5′ to 3′ translocation on the lagging strand template allows it to unwind DNA ahead of the lagging strand polymerase.
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This ensures proper coordination between helicase activity, primer synthesis, and DNA polymerase function.
Summary Table
| Option | Description | Correctness |
|---|---|---|
| (1) | 5′ → 3′ direction along lagging strand template | Correct |
| (2) | 3′ → 5′ direction along lagging strand template | Incorrect |
| (3) | 5′ → 3′ direction along leading strand template | Incorrect |
| (4) | 3′ → 5′ direction along leading strand template | Incorrect |
Conclusion
The major DNA unwinding helicase DnaB in E. coli translocates along the lagging strand template in the 5′ to 3′ direction during DNA replication. This directionality is essential for unwinding the DNA duplex ahead of the replication fork and coordinating lagging strand synthesis.
Answer:
The correct option is (1) 5′ → 3′ direction along the lagging strand template.
33 Comments
Manisha choudhary
July 25, 2025🔥🔥🔥🔥
Diksha chhipa
July 29, 2025DNA B is also known as helicase and it is bind of lagging strand of dna in 5to 3prime direction
Mansukh Kapoor
July 29, 2025The correct answer is 1 that DNa B (Helicase) binds with lagging strand of the direction of 5′—-3′
Khushi Agarwal
July 29, 2025Helicase (dna B) binds on lagging strand along 5′ to 3′ dirn
Payal Gaur
July 29, 2025In prokaryotes Helicase (dna-b) bind on 5′ to 3′ direction (lagging strand)
anurag giri
July 29, 2025Ans 1 DnaB(helicase ) binds in prokaryotes on lagging strand 5 to 3 directions
Surbhi Rajawat
July 29, 2025Helicase in eukaryotes loads on lagging strand along 5 prime to 3 prime
Vanshika Sharma
July 29, 2025Ans 1 is correct
HIMANI FAUJDAR
July 29, 2025In prokaryotes Dnb binds at 5′-3′ direction along lagging strand which unwind the DNA strand in DNA replication so answer 1 is correct
Heena
July 29, 2025DnaB loads on lagging strand in the direction of 5 to 3
Priti Khandal
July 29, 2025Right option is a because hnelicase bind with 5 se 3 in lagging strand
Priya Khandal
July 29, 2025Option A is right just because helicase helicase bind with 5’3′ Prime in leggingg stand
shruti sharma
July 29, 2025dna b is(helicase), in prokaryotes on lagging direction in 5’to 3′
Monika jangid
July 29, 2025Another name of helicase is dna B bind on lagging strand in 5′ to 3′ direction
Priya Dhakad
July 30, 2025In E. coli, the DNAB is bind with 5′-3′ in lagging strand.
Sneha Kumawat
July 30, 2025Helicase legging stand ke template par 5′ to3 direction mein translocate karke DNA ko unwind karta hai
Aafreen
July 30, 2025DNA B is another name of Helicase and in prokaryotes Helicase loads on lagging strand along 5′ – 3′ so 1st is correct answer
Niti tanwar
July 30, 2025Answer 1 bcz helicase bind with lagging strand 5′-3′ direction
Deepika Sheoran
July 30, 2025DnaB(Halicase binds with lagging strand of the direction of 5’_3′).
Pratibha Sethiya
July 30, 2025Correct option is option (1)
Bcz in prokaryotes helicase binds with lagging strand. And. In eukaryotes in leading strand
Aman Choudhary
July 30, 2025Option A is correct 5′-3′ direction along the lagging strand DNA template
Khushi Vaishnav
July 31, 20255′- 3′ direction along lagging strand template
Dipti Sharma
July 31, 2025The correct option (1) 5′ → 3′ direction along the lagging strand template.
Helicase load at lagging strand in prokaryotes and leading in eukaryotes.
Dharmpal Swami
August 1, 2025Helicase in prokaryotes bind with legging strand and in eukaryotes bind with leading strand
Khushi Mehra
August 1, 2025In prokaryotes,Helicase (dna b ) binds to lagging strand in 5′-3′ direction while in eukaryotes Helicase binds to leading strand .
Khushi Mehra
August 1, 2025In prokaryotes, Helicase binds to lagging strand in 5′-3′ direction while in eukaryotes, Helicase binds to leading strand.
Khushi Mehra
August 1, 2025In prokaryotes, Helicase binds to lagging strand in 5′-3′ direction while in eukaryotes, Helicase binds to leading strand and okazaki fragments are synthesized on lagging strand.
Vijay Marmat
August 2, 2025Done ✔️ 1
Soniya Shekhawat
August 3, 20251st is correct bcz in prokaryotes dnaB that is helicase load on lagging stand in direction of 5 prime to 3 prime.
Swati Choudhary
August 4, 2025First answer is correct DNA-B loads on lagging strand in direction of 5’-3’————>
Anita Choudhary
August 28, 2025DNA B is also known as helicase and it is bind of lagging strand of dna in 5′-3’prime direction.
Alec
August 30, 2025Dna B also known as helicase translocates in 5′ -3 direction along the lagging strand.
Deepika Sheoran
November 6, 2025DNA (B) helicase binds with lagging strand of the direction of 5′-3′