Before You Begin
Question #45873
The Question
A hypothetical primitive prebiotic cell from the 'RNA-world' era is discovered to replicate its genetic material via a strictly conservative mechanism. Scientists culture this cell in a heavy isotope medium (15N) for several generations until its genetic material is fully labeled. It is then transferred to a normal (14N) medium and allowed to replicate for exactly two generations. Upon subjecting the extracted genetic material to CsCl density gradient centrifugation, which of the following banding patterns will be observed?
Options
- A.
One intermediate (hybrid) band and one light band in equal proportions.
- B.
One heavy band and one light band, with the light band containing 75% of the total genetic material.
- C.
Only one intermediate (hybrid) band containing 100% of the genetic material.
- D.
One heavy band, one intermediate band, and one light band in a 1:2:1 ratio.
Check Your Answer
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
Meselson-Stahl Density Gradient|Evolutionary Chronology|Abiogenesis vs Biogenesis
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students are conditioned to reflexively apply the Meselson-Stahl semi-conservative results (hybrid bands) whenever they see 15N/14N and CsCl centrifugation.
The trap lies in failing to adjust the mathematical model for a 'conservative' replication mechanism.
By shifting the evolutionary chronology to a primitive system, the question tests if the student actually understands the mechanics of the replication models rather than just memorizing the NCERT E. coli results.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Molecular Basis of Inheritance - Class 12 |
| Concept | Meselson-Stahl Density Gradient |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |