Before You Begin
Question #45870
The Question
A researcher adapts the isotopic labeling principles of the Hershey-Chase experiment to study a eukaryotic DNA virus with highly split genes. Host cells are cultured in a 32P-rich medium during active viral transcription. The researcher isolates newly synthesized viral primary transcripts (hnRNA) from the nucleus and mature viral mRNA from the cytoplasm. They observe that the mature mRNA exhibits significantly lower 32P radioactivity per molecule compared to the hnRNA. Which of the following best explains this quantitative disparity?
Options
- A.
Spliceosome-mediated excision of introns removes a substantial portion of the 32P-labeled ribonucleotides prior to nuclear export.
- B.
The addition of a 7-methylguanosine cap and a poly-A tail dilutes the isotopic concentration of the transcript.
- C.
The degenerate nature of the genetic code allows the mature mRNA to be shorter than the genomic template.
- D.
32P is consumed during the formation of peptide bonds when the mRNA is translated into viral capsids.
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
Pre-mRNA|Exons|Introns|Isotopic_Tracking
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: This question forces students to synthesize the biochemical mechanism of isotopic labeling (32P in phosphodiester bonds) with the structural reality of eukaryotic split genes.
The common misconception is treating eukaryotic mRNA synthesis as a direct 1:1 stoichiometric copy of the DNA template, failing to account for the massive physical loss of nucleotides (and thus, the isotope) during intron splicing.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Molecular Basis of Inheritance - Class 12 |
| Concept | Hershey-Chase Isotopic Labeling |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |