Q.103 Botany ⭐ 360° Option Elimination Active

NEET 2023 Botany Question 103 Solution

Topic: Principles of Inheritance and Variation · Official NTA Booklet Code G5

Question

Frequency of recombination between gene pairs on same chromosome as a measure of the distance between genes to map their position on chromosome, was used for the first time by

(1)Henking
(2)Thomas Hunt Morgan
(3)Sutton and Boveri
(4)Alfred Sturtevant

✓

Verified Against NTA Final Answer Key

Option (4) : Alfred Sturtevant

📚 Principles of Inheritance and Variation Easy

📋 Given Parameters & Problem Setup

Genetic Concept Chromosome mapping using recombination frequency

Relationship 1% recombination = 1 map unit (centiMorgan)

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The 30-Second Exam Hall Shortcut: ⚡ Student of Morgan Anchor: Sturtevant = Genetic Maps

⏱️ Save ~20 seconds

T.H. Morgan established sex linkage and recombination in Drosophila, but it was his brilliant undergraduate student Alfred Sturtevant who first used recombination frequency to construct chromosome genetic maps!

1 Henking discovered the X-body in insects.

2 Sutton and Boveri formulated the Chromosomal Theory of Inheritance.

3 T.H. Morgan conducted experimental verification of linkage.

4 Alfred Sturtevant utilized recombination frequencies to generate genetic maps.

5 Match Option (4) directly.

🛡️

Why You Can 100% Trust This Shortcut: Canonical NCERT Genetics historical discovery chronology.

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Concept of Genetic Mapping

Alfred Sturtevant (1913), a student of Thomas Hunt Morgan, reasoned that the frequency of recombination between two linked gene pairs is proportional to the physical distance separating them on the chromosome:

\text{Map Distance (cM)} = \text{Recombination Frequency (\%)} = \frac{\text{Total Recombinant Offspring}}{\text{Total Offspring}} \times 100

Step 2

Historical Attribution of Related Genetic Discoveries

Key genetic milestones in NCERT include:

\begin{aligned} \text{Henking (1891):} & \quad \text{Observed X-body in insect spermatogenesis} \\[3pt] \text{Sutton \& Boveri (1902):} & \quad \text{Chromosomal Theory of Inheritance} \\[3pt] \text{T. H. Morgan (1910):} & \quad \text{Experimental proof of linkage in } \textit{Drosophila} \\[3pt] \text{\textbf{Alfred Sturtevant (1913):}} & \quad \text{\textbf{First chromosome map using recombination frequencies}} \end{aligned}

Step 3

Modern Significance

Sturtevant's genetic mapping principle served as the foundation for modern genome sequencing projects, including the Human Genome Project.

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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:

Hermann Henking discovered the nuclear structure termed the "X-body" (X-chromosome) during insect spermatogenesis, not gene maps.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing chromosome discovery with gene mapping.

2 2

✗ Incorrect

Verdict & Scientific Reason:

Morgan discovered linkage and crossing over, but his student Sturtevant constructed the first genetic map.

⚠️

Student Fallacy (Why candidates pick this trap): Attribute all Drosophila linkage discoveries to lab head Morgan instead of student Sturtevant.

3 3

✗ Incorrect

Verdict & Scientific Reason:

Walter Sutton and Theodor Boveri proposed the Chromosomal Theory of Inheritance by correlating Mendelian factors with chromosome segregation.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing chromosomal theory with genetic distance measurement.

4 4

✓ 100% Correct

Verdict & Scientific Reason:

Alfred Sturtevant utilized recombination frequency as a measure of genetic distance to map gene positions on chromosomes.

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Why this is airtight: None; verbatim textbook fact.

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NTA Trap Alert: Morgan vs. Sturtevant Trap

Because T.H. Morgan is the father of experimental genetics, students impulsively select Morgan without reading the specific mention of chromosome mapping.

🛡️ How to avoid the -1 mark: Remember: Linkage = Morgan; Gene Mapping = Sturtevant.

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Core NEET Syllabus Standard

NCERT Biology · Principles of Inheritance and Variation Standard Benchmark

Core Scientific Principle Tested:

"Alfred Sturtevant used the frequency of recombination between gene pairs on the same chromosome as a measure of the distance between genes and mapped their position on the chromosome."

Syllabus Focus: Linkage and Recombination

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

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NEET 2023 Botany Question 103 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Student of Morgan Anchor: Sturtevant = Genetic Maps

Step-by-Step Rigorous Workflow & Mathematical Proof

Concept of Genetic Mapping

Historical Attribution of Related Genetic Discoveries

Modern Significance

360° Option Elimination Engine Key Feature

NTA Trap Alert: Morgan vs. Sturtevant Trap

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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