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Question #45882
The Question
In a mutant strain of E. coli, the primary DNA-dependent DNA polymerase undergoes a structural change that completely abolishes its 3' → 5' exonuclease activity, while its 5' → 3' polymerase activity remains fully functional. What will be the most direct consequence of this mutation during the replication of the lagging strand?
Options
- A.
RNA primers will remain attached to the 5' ends of Okazaki fragments, preventing DNA ligase from sealing the nicks.
- B.
Okazaki fragments will be synthesized and ligated, but the resulting DNA will exhibit a drastically increased frequency of point mutations.
- C.
The polymerase will synthesize DNA in the 3' → 5' direction to bypass the mismatched bases, causing replication fork arrest.
- D.
DNA ligase will fail to form phosphodiester bonds between the fragments because it strictly requires a proofread, complementary 3'-OH terminus.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
DNA Polymerase Directionality|Okazaki Fragment Logic|Point Mutation
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between the specific directionalities of DNA polymerase activities (5' → 3' synthesis vs. 3' → 5' proofreading vs. 5' → 3' primer removal).
The trap lies in assuming DNA ligase acts as a secondary fidelity checkpoint or confusing the exonuclease directions.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Molecular Basis of Inheritance - Class 12 |
| Concept | Okazaki Fragment Logic |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |