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Question #45830
The Question
In human genetics, polygenic traits exhibit a continuous bell-shaped distribution. However, genomic mapping often reveals that variations within the coding sequences of the involved genes cannot fully account for the observed phenotypic spectrum. Based on the findings of the Human Genome Project, which of the following best explains this 'missing heritability'?
Options
- A.
Variations in Expressed Sequence Tags (ESTs) that alter the primary amino acid sequence of the polygenic products.
- B.
Polymorphisms in large swathes of non-coding repetitive DNA that act as cis-regulatory elements to fine-tune polygene expression.
- C.
The presence of pleiotropic genes where a single mutant allele epistatically masks the additive effect of multiple polygenes.
- D.
High mutation rates in the structural genes of the operons that control the quantitative trait.
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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
Polygenic Inheritance Curve|Human Genome Repetitive DNA|Gene Expression Control
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize the NCERT line that 'repetitive DNA has no direct coding function' and falsely equate this to 'has no function at all' (junk DNA).
They fail to synthesize this with regulatory genomics, where non-coding repetitive DNA acts as crucial regulatory elements for eukaryotic gene expression.
Additionally, the question tests the ability to differentiate between eukaryotic regulatory mechanisms and prokaryotic operons (Option D), and distinguishes between transcribed sequences (ESTs) and non-coding regulatory sequences.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Principles of Inheritance and Variation - Class 12 |
| Concept | Polygenic Inheritance Curve |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |