Q.139 Botany ⭐ 360° Option Elimination Active

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NEET 2021 Botany Question 139 Solution

Topic: Molecular Basis of Inheritance · Official NTA Booklet Code M1

Question

Identify the correct statement.

(1)In capping, methyl guanosine triphosphate is added to the 39 end of hnRNA.
(2)RNA polymerase binds with Rho factor to terminate the process of transcription in bacteria.
(3)The coding strand in a transcription unit is copied to an mRNA.
(4)Split gene arrangement is characteristic of prokaryotes.

✓

Verified Against NTA Final Answer Key

Option (2) : RNA polymerase binds with Rho factor to terminate the process of transcription in bacteria.

📚 Molecular Basis of Inheritance Easy

📋 Given Parameters & Problem Setup

Process Transcription in bacteria and eukaryotes

Target Identify the statement that is CORRECT

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The 30-Second Exam Hall Shortcut: ⚡ Sigma (σ) Initiates, Rho (ρ) Terminates Bacterial Transcription!

⏱️ Save ~20 seconds

In bacteria, the core RNA polymerase enzyme associates transiently with initiation factor Sigma ( $\sigma$ ) to start transcription and with termination factor Rho ( $\rho$ ) to terminate transcription and release the nascent RNA transcript! Statement (2) is 100% correct. Match Option (2)!

1 Check Statement (1): Capping adds methyl guanosine triphosphate to the 5' end, NOT the 3' end

\implies

INCORRECT.

2 Check Statement (2): RNA polymerase binds with Rho (

\rho

) factor to terminate transcription in bacteria

\implies

CORRECT.

3 Check Statement (3): The template strand (not coding strand) is copied to synthesize mRNA

\implies

INCORRECT.

4 Check Statement (4): Split gene arrangement (introns + exons) is characteristic of eukaryotes, NOT prokaryotes

\implies

INCORRECT.

5 Match Option (2).

🛡️

Why You Can 100% Trust This Shortcut: Canonical NCERT Molecular Basis of Inheritance on Transcription.

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Bacterial Transcription Machinery and Auxiliary Factors

In prokaryotes (bacteria), a single DNA-dependent RNA polymerase catalyzes the transcription of all three types of RNA ( $mRNA, tRNA, rRNA$ ). Although the core enzyme is capable of elongation, it requires specific accessory protein factors for initiation and termination:

\begin{aligned} \text{\textbf{Initiation:}} & \quad \text{Core RNA Polymerase} + \boldsymbol{\sigma} \text{ (Sigma factor)} \longrightarrow \text{Promoter recognition and Initiation} \\[4pt] \text{\textbf{Elongation:}} & \quad \text{Core RNA Polymerase alone catalyzes rapid chain elongation} \\[4pt] \text{\textbf{Termination:}} & \quad \text{Core RNA Polymerase} + \boldsymbol{\rho} \text{ (Rho factor)} \longrightarrow \mathbf{\text{Transcript Release and Termination}} \end{aligned}

Step 2

Refutation of False Statements

- Option (1): Capping involves adding an unusual nucleotide—methyl guanosine triphosphate—to the $5'-end$ of $hnRNA$ (polyadenylation/tailing occurs at the $3'-end$ ). - Option (3): The strand that acts as a template during transcription is the template strand ( $3' \to 5'$ ), whereas the coding strand ( $5' \to 3'$ ) has the same sequence as the newly synthesized RNA (except thymine is replaced by uracil). - Option (4): The split-gene arrangement (interrupted by non-coding introns) is a diagnostic feature of eukaryotes; prokaryotes have continuous coding cistrons.

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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 1

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. In capping, methyl guanosine triphosphate is added to the 5' end of hnRNA.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing 5' capping with 3' polyadenylation (tailing).

2 2

✓ 100% Correct

Verdict & Scientific Reason:

This statement is scientifically and canonically TRUE. Association with Rho factor terminates transcription.

💡

Why this is airtight: None. Textbook principle.

3 3

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. The template strand (3'->5') is copied by complementary base pairing, not the coding strand.

⚠️

Student Fallacy (Why candidates pick this trap): Misunderstanding the definition of template vs coding strands.

4 4

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Split genes with exons and introns are exclusive to eukaryotes.

⚠️

Student Fallacy (Why candidates pick this trap): Assuming bacteria contain spliced intron-exon split genes.

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NTA Trap Alert: 5' vs 3' End Modification Confusion in Eukaryotic Post-Transcriptional Processing

Candidates routinely flip capping (5') and tailing (3').

🛡️ How to avoid the -1 mark: Mnemonic: "Cap goes on the Head (5'); Tail goes on the Rear (3')".

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Core NEET Syllabus Standard

NEET / NCERT Biology · Molecular Basis of Inheritance Standard Benchmark

Core Scientific Principle Tested:

"RNA polymerase is only capable of catalyzing the process of elongation. It associates transiently with initiation-factor (sigma) and termination-factor (rho) to initiate and terminate the transcription, respectively."

Syllabus Focus: Transcription: Transcription in Bacteria

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

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NEET 2021 Botany Question 139 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Sigma (σ) Initiates, Rho (ρ) Terminates Bacterial Transcription!

Step-by-Step Rigorous Workflow & Mathematical Proof

Bacterial Transcription Machinery and Auxiliary Factors

Refutation of False Statements

360° Option Elimination Engine Key Feature

NTA Trap Alert: 5' vs 3' End Modification Confusion in Eukaryotic Post-Transcriptional Processing

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

🔗 Related Questions — Molecular Basis of Inheritance

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