Q.182 Zoology ⭐ 360° Option Elimination Active

NEET 2023 Zoology Question 182 Solution

Topic: Molecular Basis of Inheritance · Official NTA Booklet Code G5

Question

Given below are two statements: Statement I: In prokaryotes, the positively charged DNA is held with some negatively charged proteins in a region called nucleoid. Statement IT: In eukaryotes, the negatively charged DNA is wrapped around the positively charged histone octamer to form nucleosome. In the light of the above statements, choose the correct answer from the options given below:

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

✓

Verified Against NTA Final Answer Key

Option (1) : Statement I incorrect but Statement II is true.

📚 Molecular Basis of Inheritance Medium

📋 Given Parameters & Problem Setup

Statement I In prokaryotes, positively charged DNA is held with negatively charged proteins in nucleoid.

Statement II In eukaryotes, negatively charged DNA is wrapped around positively charged histone octamer to form nucleosome.

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The 30-Second Exam Hall Shortcut: ⚡ DNA Charge Inversion Alert: DNA is ALWAYS Negatively Charged!

⏱️ Save ~25 seconds

DNA is universally negatively charged due to its phosphate ( $PO_4^{3-}$ ) groups! Statement I claims "positively charged DNA is held with negatively charged proteins"—this inverts both charges completely and is FALSE! Statement II is TRUE (nucleosome). Select Option (1)!

1 Check Statement I: Claims DNA is positively charged and held by negatively charged proteins -> False! (DNA is negatively charged, proteins are positively charged polyamines/non-histones).

2 Check Statement II: Negatively charged DNA wrapped around positively charged histone octamer = nucleosome -> Verbatim NCERT, True.

3 Statement I is incorrect but Statement II is true.

4 Match Option (1).

🛡️

Why You Can 100% Trust This Shortcut: Canonical NCERT Molecular Genetics DNA chemical structure and packaging electrostatics.

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Electrostatic Basis of DNA Packaging

Every phosphodiester linkage in the DNA backbone carries a net negative charge at physiological pH due to ionization of the phosphate group ( $PO_4^{3-}$ ):

\text{DNA Backbone} \implies \mathbf{\text{Universally Negatively Charged (due to Phosphate groups)}}

Step 2

Evaluation of Statement I (Prokaryotic Nucleoid Packaging)

In prokaryotes (e.g., $\textit{E. coli}$ ), lacking histones, the negatively charged DNA is held in large loops by positively charged non-histone polyamine proteins in a region termed the nucleoid. Statement I states "positively charged DNA is held with negatively charged proteins", which is a complete polarity inversion and unambiguously FALSE.

\text{Prokaryotic Nucleoid} = \mathbf{\text{Negatively Charged DNA}} + \mathbf{\text{Positively Charged Proteins}} \implies \text{Statement I is } \mathbf{\text{INCORRECT}}

Step 3

Evaluation of Statement II (Eukaryotic Nucleosome)

In eukaryotes, basic proteins rich in lysine and arginine residues (histones) form an octamer bearing positive charges on their side chains. Approximately 200 bp of negatively charged DNA wraps around this core:

\mathbf{\text{Nucleosome}} = 200\text{ bp Negatively Charged DNA} + \mathbf{\text{Positively Charged Histone Octamer}} \implies \text{Statement II is } \mathbf{\text{TRUE}}

⭐

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 1

✓ 100% Correct

Verdict & Scientific Reason:

Statement I falsely inverts the electrostatic charges of DNA and proteins; Statement II accurately describes the eukaryotic nucleosome.

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Why this is airtight: None; rigorous molecular electrostatic literacy.

2 2

✗ Incorrect

Verdict & Scientific Reason:

Statement I is false because DNA is never positively charged.

⚠️

Student Fallacy (Why candidates pick this trap): Failing to notice the inverted "positively charged DNA" in Statement I.

3 3

✗ Incorrect

Verdict & Scientific Reason:

Statement II is a fundamental verified principle of chromatin biology.

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Student Fallacy (Why candidates pick this trap): Doubting whether histone octamers are positively charged.

4 4

✗ Incorrect

Verdict & Scientific Reason:

Both statement verdicts are completely reversed.

⚠️

Student Fallacy (Why candidates pick this trap): Gross misunderstanding of nucleic acid biochemistry.

⚠️

NTA Trap Alert: Subtle Charge Polarity Swap Trap

NTA replaced "negatively charged DNA" with "positively charged DNA" in Statement I. Students reading rapidly recognize the words "DNA", "proteins", and "nucleoid" and assume the sentence is true.

🛡️ How to avoid the -1 mark: Always verify charges: DNA is ALWAYS NEGATIVE (phosphates); Packaging proteins are ALWAYS POSITIVE (basic residues/polyamines).

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Core NEET Syllabus Standard

NCERT Biology · Molecular Basis of Inheritance Standard Benchmark

Core Scientific Principle Tested:

"In prokaryotes, negatively charged DNA is held with positively charged proteins in a nucleoid. In eukaryotes, negatively charged DNA wraps around positively charged histone octamer forming nucleosome."

Syllabus Focus: Packaging of DNA Helix

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

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NEET 2023 Zoology Question 182 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ DNA Charge Inversion Alert: DNA is ALWAYS Negatively Charged!

Step-by-Step Rigorous Workflow & Mathematical Proof

Electrostatic Basis of DNA Packaging

Evaluation of Statement I (Prokaryotic Nucleoid Packaging)

Evaluation of Statement II (Eukaryotic Nucleosome)

360° Option Elimination Engine Key Feature

NTA Trap Alert: Subtle Charge Polarity Swap Trap

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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