- The followjng statements are made with reference to the replication of DNA.
- The eukaryotic counterpart of the bacterial B- clamp protein is proliferating cell nuclear antigen (PCNA)
- Mutation inactivating one of the subunits of the Mcm 2-7 complex negatively affects the initiation of DNA replication in eukaryotes, but has no effect on elongation of the replication fork
- All DNA polymerases responsible for replicating the eukaryotic genome catalyze DNA chain extension in a DNA template- dependent manner.
- The FENI protein plays a role in the synthesis of the lagging strand during DNA replication as well as in base excision repair
Which one of the following options represents
INCORRECT
(1) B only (2) B and C only
(3) B and O only (4) A, B and C
Overview of the Statements
A. The eukaryotic counterpart of the bacterial β-clamp protein is proliferating cell nuclear antigen (PCNA).
B. Mutation inactivating one of the subunits of the Mcm 2-7 complex negatively affects the initiation of DNA replication in eukaryotes, but has no effect on elongation of the replication fork.
C. All DNA polymerases responsible for replicating the eukaryotic genome catalyze DNA chain extension in a DNA template-dependent manner.
D. The FEN1 protein plays a role in the synthesis of the lagging strand during DNA replication as well as in base excision repair.
Analysis of Each Statement
-
Statement A:
PCNA is indeed the eukaryotic homolog of the bacterial β-clamp, acting as a sliding clamp to increase DNA polymerase processivity. This statement is correct. -
Statement B:
The Mcm2-7 complex forms the core of the replicative helicase essential for both initiation and elongation phases of DNA replication. Mutation inactivating one subunit would impair both initiation and elongation, not just initiation. Therefore, the claim that elongation is unaffected is incorrect. -
Statement C:
DNA polymerases replicating the eukaryotic genome (e.g., Pol α, δ, ε) extend DNA strands in a DNA template-dependent manner. This is a fundamental property of DNA polymerases, making this statement correct. -
Statement D:
FEN1 (Flap Endonuclease 1) is involved in processing Okazaki fragments on the lagging strand by removing RNA primers and also functions in base excision repair pathways. This statement is correct.
Conclusion: Identifying Incorrect Statements
-
Only Statement B is incorrect because Mcm2-7 mutations affect both initiation and elongation.
-
Statements A, C, and D are correct.
Final Answer
(1) B only
Keywords
eukaryotic DNA replication, PCNA, Mcm2-7 complex, DNA polymerase, FEN1, lagging strand synthesis, DNA helicase, replication fork, DNA polymerase processivity, base excision repair
Summary Table
| Statement | Correctness | Explanation |
|---|---|---|
| A | Correct | PCNA is eukaryotic homolog of bacterial β-clamp |
| B | Incorrect | Mcm2-7 mutation affects both initiation and elongation |
| C | Correct | DNA polymerases extend DNA in template-dependent manner |
| D | Correct | FEN1 functions in lagging strand synthesis and base excision repair |
This analysis clarifies that Statement B is the only incorrect assertion among the given options regarding eukaryotic DNA replicatio
18 Comments
Priya khandal
July 28, 2025Done sir
Manisha choudhary
July 29, 2025Done sir
Pcna m mutation s initiation and elongation dono effect hote h
Eukaryotic m all dna polymerase template dependent manner m hi kaam krte h
Eukaryotic m Fen endonuclease lagging strand and base excision repair dono m kaam aata h
Non homologous k pair m
Surbhi Rajawat
July 29, 2025Only B is incorrect among all, because MCM complex is required for both initiation and elongation of replication as unwinding is continually needed
Mitali Saini
July 30, 2025Statment B is incorrect
Ankita Pareek
July 30, 2025Pcna is homolog of bacterial beta clamp
Mutation in mcm 2-7 affects both initiation and elongation
Dna polymerase extends dna in dna in template dependent manner
Flap Endonucleases remove primers and process legging stands
Swati Choudhary
July 30, 2025Only option B is wrong.
Kajal
July 30, 2025Option B is correct
Because mcm2-7 mutation cause affect in both initiation and elongation
Soniya Shekhawat
July 30, 2025Only B IS INCORRECT because mcm 2-7 is must required for dna unwind during initiation, elongation if mutation in mcm 2-7 affect both initiation and elongation
Khushi Vaishnav
July 30, 2025Statement B is incorrect because Mcm2-7 mutations affect both initiation and elongation.
Vanshika Sharma
July 30, 2025St b is incorrect bcz mcm 2-7 affect both initiaton and elongation
Sneha Kumawat
July 30, 2025B is correct .. mutation hone pr initiation and elongation affect hote h
Santosh Saini
July 30, 2025Statement B is incorrect because mcm 2-7 mutation affect both initiation and Elongation
Priti Khandal
July 30, 2025Option 1 is right
Khushi Agarwal
July 31, 2025Option b is incorrect clearly
But I hv doubt in option c bcz
Dna pol alpha is template independent
So all dna polymerase bolna glt nhi hoga??
Aafreen
July 31, 2025The Mcm 2-7 complex in eukaryotic replicative helicase and is essential for both the initiation and elongation phases of DNA replication. So only B is incorrect
Dharmpal Swami
August 1, 2025Mcm complex required for both process
shruti sharma
August 1, 2025only b is incorrect
Varsha Tatla
August 3, 2025Statement b is incorrect absolutely