Q.131 Botany ⭐ 360° Option Elimination Active

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NEET 2023 Botany Question 131 Solution

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

Question

Unequivocal proof that DNA is the genetic material was first proposed by

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Verified Against NTA Final Answer Key

Option (3) : Alfred Hershey and Martha Chase

📚 Molecular Basis of Inheritance Easy

📋 Given Parameters & Problem Setup

Discovery Unequivocal proof of DNA as genetic material

Model System Bacteriophage T2 and Escherichia coli

Radioisotopes Used ³²P (DNA phosphate) and ³⁵S (Protein methionine/cysteine)

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The 30-Second Exam Hall Shortcut: ⚡ Genetic Material Proof Hierarchy: Unequivocal = Hershey & Chase

⏱️ Save ~20 seconds

Griffith discovered transformation (1928), Avery-MacLeod-McCarty provided biochemical characterization (1944), but UNEQUIVOCAL proof was conclusively established by Alfred Hershey and Martha Chase in 1952 using radioactive isotopes ³²P and ³⁵S!

1 Griffith (1928): Transforming principle in Streptococcus pneumoniae (unproven chemical identity).

2 Avery, MacLeod, McCarty (1944): Biochemical evidence that DNA is transforming agent (not universally accepted by biologists).

3 Hershey and Chase (1952): Unequivocal proof using ³²P-DNA and ³⁵S-protein bacteriophage infection.

4 Match Option (3) Alfred Hershey and Martha Chase.

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Why You Can 100% Trust This Shortcut: Canonical NCERT Molecular Genetics historical milestone taxonomy.

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Chronology of Genetic Material Evidence

The search for the genetic material followed three landmark historical stages:

\begin{aligned} \text{Griffith (1928):} & \quad \text{Transforming principle demonstrated in } \textit{S. pneumoniae} \\[3pt] \text{Avery et al. (1944):} & \quad \text{Biochemical proof that DNA is the transforming agent} \\[3pt] \text{\textbf{Hershey \& Chase (1952):}} & \quad \mathbf{\text{Unequivocal proof using radioactive } ^{32}\text{P and }^{35}\text{S in T2 phage}} \end{aligned}

Step 2

Verbatim NCERT Association

NCERT states verbatim: "The unequivocal proof that DNA is the genetic material came from the experiments of Alfred Hershey and Martha Chase (1952). They worked with viruses that infect bacteria called bacteriophages."

Step 3

Experimental Logic

Bacteria infected with viruses grown on radioactive phosphorus ( $^{32}\text{P}$ ) were radioactive because DNA entered the host cells. Bacteria infected with viruses grown on radioactive sulfur ( $^{35}\text{S}$ ) were not radioactive, confirming that protein did not enter bacteria.

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360° Option Elimination Engine Key Feature

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4-Option Deep Scan

1 1

✗ Incorrect

Verdict & Scientific Reason:

Maurice Wilkins and Rosalind Franklin produced X-ray diffraction photographs of DNA B-form fiber.

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Student Fallacy (Why candidates pick this trap): Confusing X-ray crystallography with phage transduction experiments.

2 2

✗ Incorrect

Verdict & Scientific Reason:

Griffith observed bacterial transformation in mice but could not elucidate the chemical nature of the transforming agent.

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Student Fallacy (Why candidates pick this trap): Ignoring the qualifying descriptor "unequivocal proof".

3 3

✓ 100% Correct

Verdict & Scientific Reason:

Verbatim NCERT attribution: Hershey and Chase provided the unequivocal experimental proof that DNA is the genetic material in 1952.

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Why this is airtight: None; textbook verbatim.

4 4

✗ Incorrect

Verdict & Scientific Reason:

Avery, MacLeod, and McCarty discovered that DNA was the transforming substance, but their proof was debated until Hershey-Chase confirmed it unequivocally.

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Student Fallacy (Why candidates pick this trap): Overlooking that Avery et al.'s work was still contested by skeptics until Hershey-Chase.

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NTA Trap Alert: Avery et al. vs. Hershey & Chase "Unequivocal" Trap

Questions in NEET deliberately use the word "unequivocal" because NCERT reserves that exact adjective exclusively for Hershey and Chase.

🛡️ How to avoid the -1 mark: Keywords: "Biochemical characterisation of transforming principle" = Avery et al. "Unequivocal proof" = Hershey and Chase.

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Core NEET Syllabus Standard

NCERT Biology · Molecular Basis of Inheritance Standard Benchmark

Core Scientific Principle Tested:

"The unequivocal proof that DNA is the genetic material came from the experiments of Alfred Hershey and Martha Chase (1952)."

Syllabus Focus: The Genetic Material is DNA

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

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NEET 2023 Botany Question 131 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Genetic Material Proof Hierarchy: Unequivocal = Hershey & Chase

Step-by-Step Rigorous Workflow & Mathematical Proof

Chronology of Genetic Material Evidence

Verbatim NCERT Association

Experimental Logic

360° Option Elimination Engine Key Feature

NTA Trap Alert: Avery et al. vs. Hershey & Chase "Unequivocal" Trap

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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