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Question #45855
The Question
During a genomic analysis experiment, a researcher isolates the intact genetic material from bacteriophage ΦX174. The biochemical assay reveals the following nitrogenous base composition: Adenine = 25%, Guanine = 24%, Cytosine = 18%, and Thymine = 33%. Which of the following statements provides the most accurate biological explanation for this observation?
Options
- A.
The genome is double-stranded DNA, but high viral mutation rates cause significant deviations from Chargaff's rule of equivalence.
- B.
The genome is single-stranded DNA, hence the structural requirement for complementary base pairing and purine-pyrimidine equivalence is absent.
- C.
The genome is single-stranded RNA, which naturally lacks purine-pyrimidine parity and utilizes Thymine as a modified base.
- D.
The genome is double-stranded DNA undergoing active replication, temporarily disrupting the A+G = T+C ratio in the replication fork.
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
ΦX174_Bacteriophage|Nucleotide_Ratio|Chargaff’s_Rule_Limitation
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often rote-memorize that 'Chargaff's rule applies to DNA and not RNA' without understanding the underlying structural prerequisite: double-stranded complementarity.
The trap tests the ability to link the specific NCERT example of a single-stranded DNA virus (ΦX174) with the functional limitation of Chargaff's rule, while using the presence of Thymine to eliminate the RNA distractor.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Molecular Basis of Inheritance - Class 12 |
| Concept | Chargaff’s Rule Limitation |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |