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Question #46952
The Question
Mycoplasma possesses a minimal genome and lacks redundant replication origins, making it exceptionally vulnerable to replication arrest. During its S-phase equivalent, DNA polymerase strictly maintains a 5' to 3' polymerization directionality. Which of the following correctly explains the absolute biochemical constraint dictating this unidirectional synthesis?
Options
- A.
The enzyme requires a free 3'-OH group on the growing strand to execute a nucleophilic attack on the alpha-phosphate of the incoming dNTP.
- B.
The enzyme utilizes a free 5'-phosphate on the growing strand to execute a nucleophilic attack on the 3'-OH of the incoming dNTP.
- C.
The energy required for the phosphodiester bond formation is derived from the cleavage of the alpha and beta phosphates of the incoming dNTP.
- D.
The absence of a cell wall in Mycoplasma alters intracellular osmotic pressure, forcing DNA polymerase to rely on the 2'-OH group for polymerization.
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
Mycoplasma|Penicillin|Transpeptidase
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students memorize the '5' to 3' direction' rule from NCERT but often fail to understand the underlying biochemical necessity.
The trap tests the exact molecular interaction (3'-OH attacking the alpha-phosphate) and the dual role of dNTPs (where beta and gamma phosphates are cleaved for energy).
It also integrates the structural reality of DNA (lack of 2'-OH) and the vulnerability of minimal genomes.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biological Classification - Class 11 |
| Concept | Mycoplasma Sensitivity |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |