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Question #45869
The Question
In a modified Hershey-Chase experiment, a researcher infects E. coli with T2 bacteriophages. However, the E. coli strain used is genetically modified to hyper-express a potent restriction endonuclease that rapidly degrades the injected viral genome into short oligonucleotides, which subsequently leak out of the host cells before the blending step. Following standard blending and centrifugation, what anomalous distribution of radioactivity will be observed, and what erroneous conclusion could be drawn?
Options
- A.
Both 32P and 35S are detected primarily in the supernatant; falsely concluding that neither DNA nor protein enters the host to act as the genetic material.
- B.
32P is detected in the pellet and 35S in the supernatant; correctly concluding that DNA is the genetic material, as restriction enzymes do not affect centrifugation.
- C.
35S is detected in the pellet and 32P in the supernatant; falsely concluding that protein is the genetic material that enters the bacterial cell.
- D.
Both 32P and 35S are detected primarily in the pellet; falsely concluding that the restriction endonuclease caused the viral protein coat to enter the host cell.
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_Ligase|Palindromic_Sequences|Radioactive_Phosphorus
Why This Question Is Tricky
Common Mistakes
The 'Conceptual Pivot' lies in understanding the physical mechanics of centrifugation in the Hershey-Chase experiment.
Students often rote-memorize '32P = pellet' without realizing that the DNA must remain as a large, intact macromolecule trapped inside the intact bacterial cell membrane to be pelleted.
By introducing restriction enzymes (linking Biotechnology with Molecular Basis of Inheritance), the physical constraint is broken, turning a biological defense mechanism into an experimental confounding variable.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Molecular Basis of Inheritance - Class 12 |
| Concept | Hershey-Chase Isotopic Labeling |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |