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Question #47459
The Question
A genetic mutation in a mammalian embryo leads to agenesis of the corpus callosum due to impaired migration and apoptosis of neural progenitor cells. Cell cycle analysis reveals that during the S-phase, there is an abnormal accumulation of short DNA segments on the template strand with 5' -> 3' polarity. Which of the following statements regarding this molecular defect is INCORRECT?
Options
- A.
The accumulated short segments are Okazaki fragments, which are synthesized in the 5' -> 3' direction.
- B.
The mutation likely affects DNA ligase, an enzyme that normally catalyzes the formation of phosphodiester bonds between adjacent fragments.
- C.
The defective enzyme is responsible for establishing hydrogen bonds between the newly synthesized fragments and the template strand to ensure genomic stability.
- D.
The persistence of unligated single-strand breaks triggers apoptosis, illustrating how a molecular replication error causes macro-level anatomical defects.
Check Your Answer
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
DNA_Polymerase|Exons|Spliceosome_Mechanics|Corpus Callosum Functionality
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Bond Specificity and Enzyme Function.
Students often know that DNA ligase 'joins' or 'glues' DNA fragments together, but frequently confuse the type of bond it forms (phosphodiester vs. hydrogen).
The question also tests the direct NCERT line regarding template polarity (5' -> 3' template dictates discontinuous synthesis) and elevates it by linking a core molecular failure (unligated Okazaki fragments) to a macro-level clinical phenotype (agenesis of the corpus callosum via apoptosis).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Neural Control and Coordination - Class 11 |
| Concept | Corpus Callosum Functionality |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |