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Question #45898
The Question
A point mutation occurs at the third base (3' end) of an mRNA codon. In the cytosolic translation system, this results in a silent mutation due to the degeneracy of the genetic code and the Wobble hypothesis. However, when a similar substitution occurs in a mitochondrial gene, it leads to a stalled translation and a mutant phenotype. Which of the following best explains this phenomenon?
Options
- A.
The mitochondrial genetic code is completely non-degenerate, meaning every codon codes for a unique amino acid.
- B.
Mitochondria have a restricted number of isoacceptor tRNAs, so a codon change that is 'silent' in the cytoplasm may lack an available tRNA in the organelle.
- C.
The Wobble hypothesis is strictly applicable only to the 5' end of the anticodon in mitochondrial tRNAs, unlike cytosolic tRNAs.
- D.
Mitochondrial ribosomes lack the peptidyl transferase activity required to bypass mismatched wobble base pairs.
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
tRNA|Degeneracy|Genetic Code|mRNA
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize that '3rd base mutations are always silent due to degeneracy' without understanding that degeneracy relies on the physical availability of isoacceptor tRNAs.
The trap is assuming the universal genetic code's redundancy applies equally to the highly constrained mitochondrial translation system, which NCERT notes has exceptions to the universal code.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Molecular Basis of Inheritance - Class 12 |
| Concept | Genetic Code Degeneracy |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |