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Question #45410
The Question
A female patient diagnosed with Turner's syndrome (45, XO) presents with rudimentary ovaries, short stature, and an altered endocrine profile. In normal females (46, XX), one X chromosome is typically inactivated (forming a Barr body) to maintain gene dosage equivalence with males. Which of the following statements correctly explains why the loss of one X chromosome in Turner's syndrome causes severe endocrine and phenotypic anomalies despite the normal occurrence of X-inactivation in XX females?
Options
- A.
The entire X chromosome remains transcriptionally active in the target endocrine tissues of normal females, whereas the required hormone receptors are completely absent in Turner's syndrome.
- B.
Haploinsufficiency occurs because genes located in the pseudoautosomal regions (PAR) normally escape X-inactivation, reducing the dosage of critical developmental and receptor proteins in 45, XO individuals.
- C.
The absence of the second X chromosome alters the cellular location of steroid hormone receptors from the nucleus to the cytoplasm, preventing target gene expression.
- D.
Turner's syndrome represents a case of polyploidy where the altered ratio of autosomes to sex chromosomes directly inhibits the secretion of gonadotropins from the anterior pituitary.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Comparative_Analysis
Sharpen your ability to evaluate multiple scenarios and distinguish between competing potential answers.
Concepts Behind This Question
Turner_Syndrome|Estrogen_Receptor|Gene_Dosage_Effect
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize that 'one X chromosome is inactivated in females' but fail to reconcile this with why 45, XO (Turner's) presents a diseased phenotype.
The pivot is understanding that X-inactivation is incomplete (PAR genes escape) and that the 'gene dosage' (haploinsufficiency) of these specific escaping genes dictates the endocrine phenotype.
Furthermore, Option D tests the critical NCERT distinction between Aneuploidy (loss/gain of individual chromosomes due to non-disjunction) and Polyploidy (failure of cytokinesis leading to extra sets of chromosomes).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Chemical Coordination and Integration - Class 11 |
| Concept | Hormone Receptors Location |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |