Q.172 Zoology ⭐ 360° Option Elimination Active

NEET 2025 Zoology Question 172 Solution

Topic: Biotechnology: Principles and Processes · Official NTA Booklet Code 45

Question

Which of the following enzyme(s) are NOT essential for gene cloning? A. Restriction enzymes B. DNA ligase C. DNA mutase D. DNA recombinase E. DNA polymerase Choose the correct answer from the options given below:

✓

Verified Against NTA Final Answer Key

Option (1) : C and D only

📚 Biotechnology: Principles and Processes Easy

📋 Given Parameters & Problem Setup

Enzymes Listed A. Restriction enzymes, B. DNA ligase, C. DNA mutase, D. DNA recombinase, E. DNA polymerase

Target Enzymes that are NOT essential for gene cloning

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The 30-Second Exam Hall Shortcut: ⚡ Gene Cloning Tool Enzymes Fingerprint

⏱️ Save ~25 seconds

The core essential enzymes for gene cloning in rDNA technology are: Restriction Endonucleases (molecular scissors, A), DNA Ligase (molecular glue, B), and DNA Polymerase (PCR amplification, E)! "DNA mutase" (C) and "DNA recombinase" (D) are NOT essential cloning tools! C and D only!

1 Recall the essential enzymatic tools for recombinant DNA technology from NCERT Section 11.2:

2 - Restriction enzymes (A): Cleave DNA at palindromic recognition sequences to generate sticky/blunt ends. [ESSENTIAL]

3 - DNA ligase (B): Seals phosphodiester bonds to join foreign insert DNA with vector. [ESSENTIAL]

4 - DNA polymerase (E): Synthesizes complementary strands in PCR amplification (Taq polymerase). [ESSENTIAL]

5 - DNA mutase (C): Non-standard/spurious term with no role in cloning. [NOT ESSENTIAL]

6 - DNA recombinase (D): Mediates in vivo site-specific/homologous recombination, not an essential standard in vitro gene cloning enzyme. [NOT ESSENTIAL]

7 Enzymes NOT essential = C and D only (Option 1)!

8 Select Option (1)!

🛡️

Why You Can 100% Trust This Shortcut: Cloning Vector Selectable Markers & Insertional Inactivation (NCERT Biology · Biotechnology: pBR322 ampR and tetR selection).

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Core Enzymatic Toolbox for Gene Cloning

Construction of a recombinant DNA molecule involves a defined set of biochemical catalytic tools:

• Restriction Endonucleases (A): Molecular scissors that cleave phosphodiester backbones at specific palindromic recognition sites to yield compatible fragments.
• DNA Ligase (B): Molecular glue that joins the vector DNA and source insert DNA by synthesizing covalent phosphodiester bonds between adjacent 3'-OH and 5'-phosphate termini.
• DNA Polymerase (E): Enzymes like thermostable *Taq* polymerase essential for *in vitro* exponential amplification of the target gene via Polymerase Chain Reaction (PCR).

Step 2

Evaluation of Non-Essential Enzymes (C and D)

Analyzing candidates C and D in the context of gene cloning:

• C. DNA mutase: A non-existent or irrelevant enzyme class in recombinant DNA technology. Gene cloning aims to preserve high-fidelity replication of unmutated genes, making mutases completely antithetical and non-essential.
• D. DNA recombinase: Endogenous cellular enzymes (e.g. Cre, FLP, RecA) that catalyze somatic or homologous crossing over in living cells. They are not part of the standard core tools required for *in vitro* cutting, ligating, and cloning target genes into plasmids.

Step 3

Conclusion

DNA mutase (C) and DNA recombinase (D) are NOT essential for gene cloning, matching Option (1).

\text{Essential Cloning Tools} = \{A, B, E\} \implies \text{NOT Essential} = \{C, D\}

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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. Correctly identifies DNA mutase and DNA recombinase as not belonging to the essential gene cloning toolbox.

💡

Why this is airtight: None; pristine knowledge of biotechnology tools.

2 B

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Restriction enzymes and DNA ligase are the most fundamentally essential enzymes in all of genetic engineering.

⚠️

Student Fallacy (Why candidates pick this trap): Selecting the essential enzymes instead of the non-essential ones.

3 C

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. DNA polymerase (E) is an essential enzyme (utilized in PCR and replication).

⚠️

Student Fallacy (Why candidates pick this trap): Failing to recognize DNA polymerase as an essential biotechnology enzyme.

4 D

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. DNA ligase (B) is essential for joining recombinant vectors.

⚠️

Student Fallacy (Why candidates pick this trap): Marking DNA ligase as non-essential.

⚠️

NTA Trap Alert: Reading "NOT Essential" vs "Essential"

Always read the negative operator "NOT" carefully! Restriction enzymes, ligase, and polymerase are the holy trinity of cloning tools. Mutase and recombinase are NOT part of this essential kit.

🛡️ How to avoid the -1 mark: Circle "NOT essential" and eliminate Restriction enzymes (A), Ligase (B), and Polymerase (E).

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Core NEET Syllabus Standard

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

Core Scientific Principle Tested:

"Restriction enzymes, DNA ligases, and DNA polymerases are the essential catalytic tools in gene cloning."

Syllabus Focus: Tools of Recombinant DNA Technology · Restriction Enzymes & Ligases

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

Cut (Restriction), Paste (Ligase), Copy (Polymerase) = The Big 3! Mutase & Recombinase are OUT!

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NEET 2025 Zoology Question 172 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Gene Cloning Tool Enzymes Fingerprint

Step-by-Step Rigorous Workflow & Mathematical Proof

Core Enzymatic Toolbox for Gene Cloning

Evaluation of Non-Essential Enzymes (C and D)

Conclusion

360° Option Elimination Engine Key Feature

NTA Trap Alert: Reading "NOT Essential" vs "Essential"

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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