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Question #46415
The Question
In the human genome, microsatellites (short tandem repeats) exhibit high polymorphism. During DNA replication, as the replication fork progresses through a tract of CAG repeats, a temporary dissociation and backward looping of the newly synthesized strand occurs. Assuming the cell's mismatch repair (MMR) system fails to correct this error, what will be the immediate molecular consequence and its associated clinical phenomenon?
Options
- A.
Deletion of the repeat tract, leading to a frameshift mutation and loss of function in the p53 gene.
- B.
Expansion of the repeat tract, leading to dynamic mutations and the phenomenon of genetic anticipation seen in Huntington's disease.
- C.
Substitution of a single base pair, leading to a missense mutation characteristic of Sickle cell anemia.
- D.
Inversion of the repeat sequence, leading to a dominant negative mutation and subsequent chromosomal non-disjunction.
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
DNA Polymerase|Microsatellite Expansion|Replication Slippage
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize that repetitive DNA forms the basis of DNA fingerprinting (polymorphism) but fail to connect how this polymorphism arises mechanistically (Polymerase slippage) and its pathological extremes (Trinucleotide repeat disorders).
Furthermore, distinguishing between the looping of the template strand (causing deletion) versus the newly synthesized strand (causing expansion) tests deep conceptual clarity of replication fork dynamics.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Molecular Basis of Inheritance - Class 12 |
| Concept | Human Genome Repetitive DNA |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |