Q.162 Zoology ⭐ 360° Option Elimination Active

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NEET 2026 Zoology Question 162 Solution

Topic: Biotechnology: Principles and Processes · Official NTA Booklet Code 50

Question

During PCR, primers bind to the DNA strands in the step.

(1)denaturation
(2)extension
(3)annealing
(4)ligation

✓

Verified Against NTA Final Answer Key

Option (3) : Annealing

📚 Biotechnology: Principles and Processes Easy

📋 Given Parameters & Problem Setup

Molecular Technique Polymerase Chain Reaction (PCR)

Defined Event Binding of two sets of oligonucleotide primers to single-stranded DNA templates

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The 30-Second Exam Hall Shortcut: ⚡ PCR Triad Temperature Trap

⏱️ Save ~30 seconds

Denature (94°C) -> Anneal Primers (50-60°C) -> Extend (72°C)!

1 Recall 3 PCR steps in chronological order: Denaturation, Annealing, Extension.

2 (Denaturation): High temp separates dsDNA into single strands.

3 (Annealing): Primers bind (hybridize) to complementary regions on ssDNA templates.

4 (Extension): Taq polymerase synthesizes new DNA strands.

5 Question asks specifically for primer binding -> Annealing.

6 Select Option (3) Annealing.

🛡️

Why You Can 100% Trust This Shortcut: NCERT Biology · Biotechnology: Principles and Processes (Competent Host Preparation: Divalent cation treatment facilitates plasmid uptake).

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Mechanism of Annealing in PCR

Annealing involves the hybridization of two sets of oligonucleotide primers to the single-stranded template DNA at an optimal temperature (typically 50–60°C).

\text{ssDNA Templates} + 2 \text{ Primer Sets} \xrightarrow{50-60^\circ\text{C}} \text{Primer-Template Duplexes (Annealing)}

• Primers are small chemically synthesized oligonucleotides complementary to the regions of DNA.

Step 2

Contrast with Denaturation and Extension

Denaturation uses heat (~94°C) to break hydrogen bonds between complementary strands. Extension (~72°C) uses thermostable DNA polymerase (Taq polymerase isolated from Thermus aquaticus) and dNTPs to extend the primers.

\text{Denaturation (94}^\circ\text{C)} \rightarrow \mathbf{Annealing (54^\circ\text{C})} \rightarrow \text{Extension (72}^\circ\text{C)}

• Repeated cycles achieve billion-fold amplification (~10⁹ times).

⭐

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

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Denaturation is the thermal separation of double-stranded DNA into single strands, not primer binding.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing initial strand separation with primer binding.

2 B

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Extension is the primer elongation phase catalyzed by Taq polymerase at ~72°C.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing DNA synthesis with primer hybridization.

3 C

✓ 100% Correct

Verdict & Scientific Reason:

100% correct. Annealing is the specific PCR step where oligonucleotide primers bind to complementary single strands of DNA.

💡

Why this is airtight: None; standard PCR textbook step.

4 D

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Amplification is the overall outcome of the entire multi-cycle PCR process, not an individual step.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing overall process outcome with the specific hybridization step.

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NTA Trap Alert: Confusing Annealing with Extension

Some students confuse annealing (putting primers on) with extension (running down the track synthesizing DNA). Annealing attaches primers; extension elongates them.

🛡️ How to avoid the -1 mark: Remember: "A" comes before "E": Anneal primers first, then Extend!

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Core NEET Syllabus Standard

NEET Biology Core Syllabus · Biotechnology: Principles and Processes Standard Benchmark

Core Scientific Principle Tested:

"PCR consists of three steps: Denaturation, Annealing (primer binding), and Extension."

Syllabus Focus: Polymerase Chain Reaction (PCR)

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

D-A-E: Denature the double strand, Anneal the primer, Extend the polymer!

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NEET 2026 Zoology Question 162 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ PCR Triad Temperature Trap

Step-by-Step Rigorous Workflow & Mathematical Proof

Mechanism of Annealing in PCR

Contrast with Denaturation and Extension

360° Option Elimination Engine Key Feature

NTA Trap Alert: Confusing Annealing with Extension

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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