Before You Begin
Question #45841
The Question
A geneticist observes two distinct human disorders: Disorder X is caused by an autosomal recessive mutation leading to mental retardation and reduced skin pigmentation, while Disorder Y is characterized by short stature, furrowed tongue, and congenital heart disease due to meiotic non-disjunction. Which of the following statements regarding the genetic principles governing these disorders is INCORRECT?
Options
- A.
Disorder X demonstrates pleiotropy, where a single mutant gene affects multiple phenotypic traits.
- B.
The multi-systemic anomalies in Disorder Y represent a pleiotropic effect caused by the mutation of a single master regulatory gene on the extra chromosome.
- C.
Disorder Y is an example of aneuploidy, which alters the gene dosage of hundreds of loci simultaneously rather than mutating a single locus.
- D.
The inheritance of the gene involved in Disorder X follows Mendelian principles, whereas Disorder Y arises from a failure in chromosomal segregation during cell division.
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
Aneuploidy_vs_Polyploidy|Pleiotropy_Logic|Chromosomal_Theory_of_Inheritance
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often confuse the multi-trait manifestation of chromosomal disorders (like Down Syndrome) with pleiotropy.
The trap lies in failing to distinguish between 'multiple traits caused by one mutant gene' (Pleiotropy) and 'multiple traits caused by altered dosage of hundreds of normal genes' (Aneuploidy).
Option B exploits this by using plausible-sounding terminology ('master regulatory gene') to mask the fundamental definition of aneuploidy.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Principles of Inheritance and Variation - Class 12 |
| Concept | Aneuploidy vs Polyploidy |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |