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Question #45768
The Question
A human macrophage exhibits a complete loss of amoeboid motility. Genetic analysis reveals a trisomy of an autosome harboring genes for actin-nucleating factors. Sequence analysis of these genes shows several synonymous substitutions but no missense or nonsense mutations. Which of the following best explains the loss of amoeboid movement in this cell?
Options
- A.
Synonymous mutations in the actin-regulatory genes alter the tertiary structure of microfilaments, inhibiting pseudopodia formation.
- B.
Aneuploidy-induced gene dosage imbalance disrupts the stoichiometric ratio of actin-regulatory proteins, altering the critical concentration for microfilament treadmilling.
- C.
The degeneracy of the genetic code fails to buffer the extra chromosomal copy, leading to the synthesis of non-functional, truncated tubulin proteins.
- D.
The trisomic condition directly inhibits the ATPase activity of dynein arms, which are essential for the sol-gel transformation during amoeboid movement.
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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
Genetic_Code_Degeneracy|Aneuploidy|Amoeboid_Movement
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students must integrate three distinct NCERT concepts: (1) Amoeboid movement relies on microfilaments (Locomotion and Movement), (2) Degeneracy of the genetic code results in silent mutations (Molecular Basis of Inheritance), and (3) Aneuploidy causes gene dosage effects (Principles of Inheritance).
The trap lies in confusing the cytoskeletal elements (microfilaments vs. microtubules) and assuming that if a protein's sequence is normal (due to degeneracy), the cellular function must remain normal, ignoring the quantitative disruption caused by aneuploidy.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Locomotion and Movement - Class 11 |
| Concept | Amoeboid Movement Mechanism |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |