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Question #47476
The Question
A male child with a karyotype of 47, XY, +21 exhibits significant retardation in psychomotor development. While his ability to initiate voluntary movements is intact, he profoundly struggles with fine motor precision, equilibrium, and complex coordinated tasks. Which of the following neuroanatomical anomalies, driven by dosage-sensitive gene expression, best explains this specific clinical presentation?
Options
- A.
Cerebellar hypoplasia and reduced dendritic arborization of Purkinje cells.
- B.
Global cerebral atrophy leading to a failure in generating voluntary motor commands.
- C.
Agenesis of the corpus callosum preventing the integration of sensory-motor pathways.
- D.
Degeneration of the basal ganglia resulting in altered muscle tone and resting tremors.
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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
Cerebellum|Developmental Biology|Karyotype|Genetic neurological expression
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often conflate the 'mental retardation' of Down syndrome with global brain failure, missing the NCERT keyword 'psychomotor'.
By isolating the deficit to 'precision and equilibrium' while 'initiation' remains intact, the question forces the student to bypass the cerebrum and identify the cerebellum as the specific neuroanatomical target of the aneuploid gene dosage effect.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Neural Control and Coordination - Class 11 |
| Concept | Cerebellar Coordination Dynamics |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |