Q.136 Zoology ⭐ 360° Option Elimination Active

NEET 2025 Zoology Question 136 Solution

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

Question

Given below are two statements: Statement I: The DNA fragments extracted from gel electrophoresis can be used in construction of recombinant DNA. Statement II: Smaller size DNA fragments are observed near anode while larger fragments are found near the wells in an agarose gel. In the light of the above statements, choose the most appropriate answer from the options given below:

(1)Both statement I and statement II are correct
(2)Both statement I and statement II are incorrect
(3)Statement I is correct but statement II is incorrect
(4)Statement I is incorrect but statement II is correct

✓

Verified Against NTA Final Answer Key

Option (1) : Both statement I and statement II are correct

📚 Biotechnology: Principles and Processes Easy

📋 Given Parameters & Problem Setup

Statement I The DNA fragments extracted from gel electrophoresis can be used in construction of recombinant DNA.

Statement II Smaller size DNA fragments are observed near anode while larger fragments are found near the wells in an agarose gel.

⚡

The 30-Second Exam Hall Shortcut: ⚡ Gel Electrophoresis Vector Fingerprint

⏱️ Save ~25 seconds

DNA is negatively charged -> migrates to positive Anode (+)! Smaller fragments slip through agarose mesh faster and reach near anode; larger fragments lag near wells (cathode)! Eluted bands are cloned into vectors! Both statements are 100% TRUE!

1 Analyze Statement I:

2 - "The separated bands of DNA are cut out from the agarose gel and extracted from the gel piece. This step is known as elution. The DNA fragments purified in this way are used in constructing recombinant DNA by joining them with cloning vectors." -> NCERT verbatim! Statement I is CORRECT.

3 Analyze Statement II:

4 - DNA is polyanionic (negative charge due to phosphate backbone). It migrates from cathode (-ve, wells) to anode (+ve).

5 - Agarose provides a molecular sieving effect: smaller fragments travel faster and further (closer to the anode), whereas larger fragments migrate slowly and remain closer to the loading wells.

6 - Statement II is CORRECT.

7 Conclusion: Both statement I and statement II are correct!

8 Select Option (1)!

🛡️

Why You Can 100% Trust This Shortcut: Gel Electrophoresis & Ethidium Bromide Staining (NCERT Biology · Biotechnology: Principles and Processes: UV illumination of orange DNA bands).

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Principle of Agarose Gel Electrophoresis (Statement II)

Separation of restriction enzyme-digested DNA fragments relies on charge-to-mass uniformity and size-dependent molecular sieving:

• DNA fragments carry uniform negative charges along their phosphate backbones and migrate towards the positive electrode (anode) when an electric field is applied.
• The matrix (agarose gel) acts as a molecular sieve: smaller fragments experience less frictional resistance and travel farther towards the anode.
• Larger fragments encounter high hydrodynamic drag and remain near the loading wells at the cathodic end.
• Hence, Statement II is completely CORRECT.

Step 2

DNA Band Visualization and Elution (Statement I)

Post-electrophoretic utilization of resolved DNA fragments in genetic engineering:

• DNA bands are visualized by staining with ethidium bromide (EtBr) under ultraviolet (UV) light as bright orange-colored bands.
• The desired DNA band is excised from the agarose gel and extracted/purified via elution.
• The purified fragment of interest is subsequently ligated into a linearized cloning vector using DNA ligase to produce recombinant DNA (rDNA).
• Hence, Statement I is completely CORRECT.

Step 3

Conclusion

Both Statement I and Statement II are factually and conceptually correct, matching Option (1).

\text{Statement I: True}, \quad \text{Statement II: True} \implies \text{Option (1)}

⭐

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. Accurately verifies both the sieving migration principle and the subsequent cloning utility of eluted DNA.

💡

Why this is airtight: None; pristine biotechnology mastery.

2 B

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Both statements represent canonical NCERT facts.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing electrophoresis polarities.

3 C

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Statement II is true (smaller fragments migrate faster towards anode).

⚠️

Student Fallacy (Why candidates pick this trap): Believing larger fragments move faster or reversing anode/cathode polarity.

4 D

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Statement I is true (eluted DNA is the standard substrate for rDNA construction).

⚠️

Student Fallacy (Why candidates pick this trap): Thinking gel-extracted DNA cannot be ligated.

⚠️

NTA Trap Alert: Anode (+) vs Cathode (-) in Electrophoresis

In electrolytic cells like gel electrophoresis, the ANODE is POSITIVE and the CATHODE is NEGATIVE. Since DNA is negatively charged, it runs TOWARDS the ANODE. The wells are at the Cathode!

🛡️ How to avoid the -1 mark: Remember: "Run to Red / Run to Anode (+)". Small fragments get there first!

📖

Core NEET Syllabus Standard

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

Core Scientific Principle Tested:

"DNA fragments migrate to the anode according to size through agarose gel; purified eluted fragments are used in constructing recombinant DNA."

Syllabus Focus: Separation and Isolation of DNA Fragments

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

Small slips to Anode (+), Elution equals rDNA construction!

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NEET 2025 Zoology Question 136 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Gel Electrophoresis Vector Fingerprint

Step-by-Step Rigorous Workflow & Mathematical Proof

Principle of Agarose Gel Electrophoresis (Statement II)

DNA Band Visualization and Elution (Statement I)

Conclusion

360° Option Elimination Engine Key Feature

NTA Trap Alert: Anode (+) vs Cathode (-) in Electrophoresis

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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