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Question #45607
The Question
A patient homozygous for a severe mutant allele of the CFTR gene (an autosomal recessive disorder) suffers from chronic malabsorption due to pancreatic duct blockage. Despite having a normal 46,XY karyotype, the patient exhibits delayed puberty, low circulating LH and FSH levels, and arrested spermatogenesis. Based on the principles of endocrine feedback and genetic pleiotropy, which of the following best explains the arrest in gametic development?
Options
- A.
Severe metabolic stress from malnutrition suppresses hypothalamic GnRH pulsatility, leading to hypogonadotropic hypogonadism and failure to stimulate meiosis.
- B.
The mutant CFTR allele exhibits pleiotropy by directly inhibiting the recombinase enzymes required for crossing over in primary spermatocytes.
- C.
Thick mucus accumulation in the seminiferous tubules physically compresses Leydig cells, preventing testosterone synthesis and meiotic progression.
- D.
Nutritional deficiency induces hypersecretion of inhibin from Sertoli cells, exerting strong negative feedback on the anterior pituitary to halt gametogenesis.
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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
Meiotic_Arrest|CFTR_Gene|Allelic_Heterogeneity
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often confuse the direct pleiotropic effects of a genetic mutation with its indirect systemic consequences.
While CFTR mutations are famous for causing male infertility via anatomical blockage (absence of vas deferens), the presence of 'low LH/FSH' in the question stem pivots the logic to an indirect endocrine failure.
The trap is assuming the genetic mutation directly halts meiosis (Option B) or physically blocks the testes (Option C), whereas the meiotic arrest here is a secondary failure of the HPG axis due to malnutrition-induced metabolic stress.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Principles of Inheritance and Variation - Class 12 |
| Concept | Multiple Allelism Limitation |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |