Q.144 Zoology ⭐ 360° Option Elimination Active

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NEET 2025 Zoology Question 144 Solution

Topic: Biotechnology and its Applications · Official NTA Booklet Code 45

Question

Silencing of specific mRNA is possible via RNAi because of -

(1)Complementary dsRNA
(2)Inhibitory ssRNA
(3)Complementary tRNA
(4)Non-complementary ssRNA

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Verified Against NTA Final Answer Key

Option (1) : Complementary dsRNA

📚 Biotechnology and its Applications Easy

📋 Given Parameters & Problem Setup

Process RNA interference (RNAi) / post-transcriptional gene silencing

Target Molecular Agent Molecule responsible for silencing specific mRNA

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The 30-Second Exam Hall Shortcut: ⚡ RNAi Trigger Fingerprint

⏱️ Save ~20 seconds

RNA interference silences target mRNA using COMPLEMENTARY DOUBLE-STRANDED RNA (dsRNA)! Cleaved by Dicer into siRNA, binds and cleaves target mRNA!

1 Recall NCERT Section 12.2 (Biotechnology Applications in Agriculture):

2 - "This method involves silencing of a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA (silencing)."

3 - The source of this complementary RNA could be from an infection by viruses having RNA genomes or mobile genetic elements (transposons).

4 - In tobacco plants, *Agrobacterium* vectors introduce nematode-specific genes producing both sense and anti-sense RNA, forming double-stranded RNA (dsRNA).

5 Direct answer: Complementary dsRNA!

6 Select Option (1)!

🛡️

Why You Can 100% Trust This Shortcut: Bt Toxin Mechanism of Insecticidal Action (NCERT Biology · Biotechnology and its Applications: Alkaline gut activation and epithelial cell lysis).

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Mechanism of RNA Interference (RNAi)

RNA interference is an evolutionarily conserved gene-regulatory and cellular defence mechanism in all eukaryotes:

• It mediates sequence-specific post-transcriptional gene silencing (PTGS) of targeted mRNA transcripts.
• The trigger for RNAi is complementary double-stranded RNA (dsRNA).
• An endoribonuclease called Dicer processes long dsRNA into short interfering RNAs (siRNAs, ~21–23 bp).
• These siRNAs incorporate into the RNA-induced silencing complex (RISC), which unwinds the duplex and guides the single-stranded antisense strand to the complementary target mRNA, causing enzymatic cleavage and degradation.

Step 2

Application in Pest-Resistant Transgenic Plants

Preventing infestation of tobacco roots by the nematode *Meloidogyne incognita*:

• Using *Agrobacterium* vectors, nematode-specific genes were introduced into the host plant.
• The introduction of DNA was such that it produced both sense and anti-sense RNA in the host cells.
• These two RNAs, being complementary to each other, annealed to form a double-stranded RNA (dsRNA) that initiated RNAi and silenced the specific mRNA of the nematode.
• Consequently, the parasite could not survive in a transgenic host expressing specific interfering RNA.

Step 3

Conclusion

The specific molecular agent responsible for mRNA silencing in RNAi is Complementary dsRNA.

\text{Silencing Trigger} = \text{Complementary dsRNA (Option 1)}

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360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan

1 A

✓ 100% Correct

Verdict & Scientific Reason:

100% correct. NCERT explicitly states: "silencing of a specific mRNA due to a complementary dsRNA molecule".

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Why this is airtight: None; textbook mastery.

2 B

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Single-stranded RNA alone does not initiate the Dicer-mediated RNAi pathway; it must be double-stranded (dsRNA).

⚠️

Student Fallacy (Why candidates pick this trap): Confusing single-stranded antisense RNA with the active dsRNA trigger.

3 C

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. tRNA functions as an adaptor in protein synthesis, not as a gene-silencing trigger in RNAi.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing tRNA codon-anticodon pairing with RNA interference.

4 D

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Non-complementary RNA cannot hybridize to target mRNA and has zero silencing capacity.

⚠️

Student Fallacy (Why candidates pick this trap): Disregarding the fundamental requirement for sequence complementarity.

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NTA Trap Alert: dsRNA vs ssRNA in RNAi

Single-stranded RNA cannot trigger the standard Dicer-RISC RNAi cascade. Both sense and antisense strands must anneal to form DOUBLE-STRANDED RNA (dsRNA) which initiates silencing!

🛡️ How to avoid the -1 mark: RNAi always requires dsRNA (double-stranded RNA).

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Core NEET Syllabus Standard

NEET Biology Core Syllabus · Biotechnology and its Applications Standard Benchmark

Core Scientific Principle Tested:

"Silencing of specific mRNA in RNAi is mediated by complementary dsRNA molecules."

Syllabus Focus: Applications in Agriculture · Pest Resistant Plants (RNAi)

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

RNAi = DOUBLE trouble for mRNA: dsRNA silences it!

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NEET 2025 Zoology Question 144 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ RNAi Trigger Fingerprint

Step-by-Step Rigorous Workflow & Mathematical Proof

Mechanism of RNA Interference (RNAi)

Application in Pest-Resistant Transgenic Plants

Conclusion

360° Option Elimination Engine Key Feature

NTA Trap Alert: dsRNA vs ssRNA in RNAi

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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