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Question #46860
The Question
In a patient suffering from progressive myonecrosis and the gradual loss of skeletal muscle striations, molecular analysis reveals the epigenetic silencing of the dystrophin gene due to altered histone-DNA interactions. Which of the following correctly describes the primary epigenetic modification and the subsequent structural failure in the muscle fiber?
Options
- A.
Histone deacetylation restores the positive charge on lysine residues, tightly coiling the DNA to silence the gene; the resulting absence of dystrophin decouples the sarcomeric actin from the sarcolemma.
- B.
Histone acetylation neutralizes the positive charge on arginine residues, loosening the DNA to silence the gene; the resulting absence of dystrophin prevents calcium release from the sarcoplasmic reticulum.
- C.
Histone phosphorylation increases the negative charge on the octamer, repressing transcription; the resulting absence of dystrophin directly degrades the myosin thick filaments in the A-band.
- D.
Histone deacetylation removes the positive charge on the octamer, enhancing heterochromatin formation; the resulting absence of dystrophin disrupts the binding of troponin to tropomyosin.
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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
Skeletal Muscle Striation Pattern|Histone Octamer Charge Interaction|Dystrophin|Myofilament Protein Composition
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: This question tests two distinct high-yield concepts simultaneously.
First, the electrostatic basis of epigenetics (students often memorize 'deacetylation = silencing' but fail to realize it works by restoring the positive charge on lysine, trapping them in Option D).
Second, the exact structural role of dystrophin (students often confuse it with contractile regulatory proteins like troponin or structural sarcomere proteins like myosin, rather than its true role as a sarcolemma anchor).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Structural Organisation in Animals - Class 11 |
| Concept | Skeletal Muscle Striation Pattern |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |