49. A mutant DNA polymerase was found to have higher error rate and synthesized only short DNA fragments. In the statements below, potential explanations are given.
A. The 5′ to 3′ exonuclease activity is compromised.
B. The 3′ to 5′ exonuclease activity is compromised.
C. The polymerase tends to frequently dissociate from the template.
D. The polymerase is unable to unwind the DNAtemplate during replication.
Which one of the following options represents the combination of all correct statements? (1) A and B (2) C and D (3) A and D (4) B and c
Key Observations About the Mutant DNA Polymerase
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Higher error rate: Indicates reduced fidelity during DNA synthesis, often due to loss of proofreading ability.
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Synthesis of short DNA fragments: Suggests poor processivity or frequent dissociation from the DNA template.
Analysis of the Given Statements
A. The 5′→3′ exonuclease activity is compromised.
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This activity mainly removes RNA primers during replication.
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Its loss affects primer removal but does not directly cause higher error rates or short fragments.
B. The 3′→5′ exonuclease activity is compromised.
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This is the proofreading activity that corrects misincorporated nucleotides.
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Loss of this activity leads to higher error rates during DNA synthesis.
C. The polymerase tends to frequently dissociate from the template.
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Frequent dissociation means low processivity, resulting in short DNA fragments synthesized before the polymerase falls off.
D. The polymerase is unable to unwind the DNA template during replication.
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DNA polymerases do not unwind DNA; helicases perform this function.
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This inability would stall replication but is not a direct cause of short fragments or higher error rate.
Correct Combination of Statements
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B (loss of 3′→5′ exonuclease proofreading activity causing higher error rate)
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C (frequent dissociation causing short DNA fragments)
Final Answer
(4) B and C
Summary Table
| Statement | Explanation | Correctness |
|---|---|---|
| A | Loss affects primer removal, not error rate or fragment length | No |
| B | Loss of proofreading increases error rate | Yes |
| C | Frequent dissociation reduces processivity, causing short fragments | Yes |
| D | Polymerase does not unwind DNA; helicase does | No |
Keywords
mutant DNA polymerase, higher error rate, short DNA fragments, 3′→5′ exonuclease, proofreading activity, polymerase processivity, DNA replication fidelity, polymerase-template dissociation
Summary:
A mutant DNA polymerase with a higher error rate and short DNA fragments likely has compromised 3′→5′ exonuclease proofreading activity leading to increased errors and tends to frequently dissociate from the DNA template, resulting in low processivity and short DNA products.
22 Comments
Manisha choudhary
July 29, 2025Done sir 👍🏻
Surbhi Rajawat
July 29, 2025Option 4 is correct. Because high error and short DNA formation occurs due to hindrance in 3′ to 5′ polymerase activity and low processivitiy
Mansukh Kapoor
July 29, 2025The correct answer is option 4th because it lacks of proof reading activity and produce short fragments of dna
Priya Khandal
July 29, 2025Option 4th is right because Iske pass Proof reading activity absent The Isliye DNA ke छोटे-छोटे fragment Milenge
Priti Khandal
July 29, 2025Done sir option 4 Is Right because 3 5 proof reading activity absent h and dna templet alag ho rahe h
anurag giri
July 30, 2025Ans 4 bcoz it have lose of proof reading activity and make shor dna fragments
Sneha Kumawat
July 30, 2025The correct answer is b and c …3 to 5 nucleus activity Lo Sone per higher error rates milati hai and kam processivity ke Karan pol baar baar dissociate hoga
Vanshika Sharma
July 30, 2025Option 4 bcz it lack proof reading activity and produce Short fragments of dna
Khushi Agarwal
July 30, 2025Ans 4 is correct
B → High error rate (proofreading defect)
C – Short fragments (low processivity)
Anisha jakhar
July 30, 2025Option 4
shruti sharma
July 30, 2025B and C
Soniya Shekhawat
July 31, 2025Option B and C bcz due to lack of 3′→5′ exonuclease proofreading and low processivity means baar baar dissociate hoga..
Santosh Saini
July 31, 2025Statement B and C are correct because higher error rate during DNA synthesis due to loss of proofreading activity and short DNA fragments synthesize by low processivity
Aafreen
July 31, 2025Ans-4
B:- its compromise would lead to a higher error rate ( proof reading)
C:- short DNA means low processivity
Aafreen
July 31, 2025Ans-4
B:- its compromise would lead to a higher error rate ( proof reading).
C:- short DNA means low processivity
kajal
July 31, 2025Option
B- loss of 3′ – 5′ exonuclease activity cause high error
C- Frequent dissociation causes short dna fragments
Khushi Vaishnav
July 31, 20253-5′ exonuclease proofreading activity leading to high errors and tends to frequently dissociate DNA template results in low processivity and short DNA .products.
Diksha Chhipa
July 31, 2025Frequently dissociation means less processivity .if 5 to 3 exonuclease activity is compromised then not high rate error occur but if 3to 5 prime exonuclease activity is compromised then wrong ntds bind and resulting this high rate of error occur
Dharmpal Swami
August 1, 2025Loss of proofreading in 3′ to 5′ exonuclease activity then error rate increase
Varsha Tatla
August 3, 2025If, dna pol. Shows high error rate it means the 3′-5’exonuclease activity is compromised
And in case of short dna fragment formation dna pol enz dissociation from templetes responsible
Deepika sheoran
August 3, 2025Option 4th is correct answer
Because proof reading Activity increase.processivity causing short fragment.
Deepika Sheoran
November 7, 2025Loss of proof reading in 3′-5′ Exonuclease Activity then error rate increase.