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Question #45405
The Question
During the embryonic development of a mammal, the differentiation of the inner cell mass (ICM) requires precise regulation of gene expression. A researcher treats a blastocyst with a chemical that completely inhibits Histone Deacetylase (HDAC) enzymes. Which of the following statements correctly describes the resulting molecular and cellular consequence?
Options
- A.
Histones will remain hyper-acetylated, neutralizing their positive charge and maintaining a euchromatin state that prevents the silencing of pluripotency genes, thereby arresting normal differentiation.
- B.
The positive charge on lysine and arginine residues of histones will increase, leading to tight packaging of DNA into heterochromatin and premature differentiation.
- C.
DNA methylation will be directly inhibited, causing the nucleosome core particle to dissociate and halting DNA replication during the cleavage stage.
- D.
The chromatin will remain in a permanently condensed state because the added acetyl groups strongly attract the negatively charged phosphate backbone of DNA.
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
Stem Cells|Histone Octamer Charge Interaction|Gene Expression
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: The electrostatic relationship between histones and DNA.
Students often memorize 'acetylation = active' but fail to understand the underlying charge mechanics (neutralization of Lys/Arg positive charges).
The trap in Option D tests the misconception that acetyl groups themselves attract DNA, while Option B tests the inverse relationship between acetylation and positive charge.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Human Reproduction - Class 12 |
| Concept | Differentiation of Stem Cells |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |