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Question #47728
The Question
During the separation of restriction endonuclease-digested DNA fragments via agarose gel electrophoresis, a student mistakenly uses a running buffer with an excessively high ionic strength (e.g., 10X concentration instead of 1X). Which of the following best describes the consequence on DNA migration and its underlying biophysical cause?
Options
- A.
Poor resolution and co-migration of different-sized fragments due to excessive shielding of the DNA's negative charge by buffer cations.
- B.
Accelerated migration of all fragments with enhanced size-based separation due to the increased electrical conductivity of the buffer.
- C.
Migration of DNA fragments towards the cathode due to the reversal of the DNA's net charge by the buffer's ionic saturation.
- D.
Complete cessation of DNA migration because the high ionic strength neutralizes the applied electric field across the gel matrix.
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
Ori_Sequence_Stringency|Selectable_Marker_vs_Cloning_Site|Replicon
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students memorize the NCERT line 'the smaller the fragment size, the farther it moves' assuming it is an absolute physical law dependent solely on the agarose sieve.
They often fail to realize that this size-based separation relies entirely on a constant charge-to-mass ratio.
By altering the buffer's ionic strength, the effective charge shielding changes, collapsing the fundamental size-resolution power of the matrix.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biotechnology : Principles and Processes - Class 12 |
| Concept | Ori Sequence Stringency |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |