Q.114 Botany ⭐ 360° Option Elimination Active

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NEET 2023 Botany Question 114 Solution

Topic: Cell Cycle and Cell Division · Official NTA Booklet Code G5

Question

The process of appearance of recombination nodules occurs at which sub stage of prophase I in meiosis?

(1)Diakinesis
(2)Zygotene
(3)Pachytene
(4)Diplotene

✓

Verified Against NTA Final Answer Key

Option (3) : Pachytene

📚 Cell Cycle and Cell Division Easy

📋 Given Parameters & Problem Setup

Division Phase Prophase I of Meiosis

Cytological Feature Appearance of recombination nodules

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The 30-Second Exam Hall Shortcut: ⚡ LZPDD Meiosis Anchor: Recombination Nodules = Pachytene

⏱️ Save ~20 seconds

Remember the five sub-stages: Leptotene (compaction), Zygotene (synapsis/synaptonemal complex), Pachytene (crossing over & recombination nodules), Diplotene (chiasmata), Diakinesis (terminalisation). Recombination nodules appear in Pachytene!

1 Zygotene: Homologous chromosomes synapse; synaptonemal complex forms.

2 Pachytene: Bivalents clearly visible as tetrads; recombination nodules appear; crossing over mediated by recombinase.

3 Diplotene: Dissolution of synaptonemal complex; X-shaped chiasmata become visible.

4 Diakinesis: Terminalisation of chiasmata.

5 Match Option (3) Pachytene.

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Why You Can 100% Trust This Shortcut: Canonical NCERT Cell Division Prophase I sub-stage cytological markers.

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Chronology of Prophase I Sub-stages

Prophase I is exceptionally prolonged and categorized into five consecutive stages based on chromosomal behavior:

\begin{aligned} \text{Leptotene:} & \quad \text{Progressive condensation and compaction of chromatin} \\[3pt] \text{Zygotene:} & \quad \text{Synapsis mediated by synaptonemal complex} \\[3pt] \text{\textbf{Pachytene:}} & \quad \text{\textbf{Recombination nodules appear; crossing over occurs}} \\[3pt] \text{Diplotene:} & \quad \text{Dissolution of synaptonemal complex; chiasmata visible} \\[3pt] \text{Diakinesis:} & \quad \text{Terminalisation of chiasmata; nuclear envelope breakdown} \end{aligned}

Step 2

Nature of Recombination Nodules

Recombination nodules are protein-rich multicomponent enzymatic complexes (containing recombinase, DNA endonucleases, and ligases) that assemble along the synaptonemal complex between non-sister chromatids of homologous chromosomes at pachytene.

Step 3

Verbatim NCERT Definition

NCERT states verbatim: "This stage is characterized by the appearance of recombination nodules, the sites at which crossing over occurs between non-sister chromatids of the homologous chromosomes."

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4-Option Deep Scan

1 1

✗ Incorrect

Verdict & Scientific Reason:

Diakinesis is the final stage marked by terminalisation of chiasmata, spindle assembly, and nucleolus disappearance.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing terminalisation of chiasmata with initial nodule assembly.

2 2

✗ Incorrect

Verdict & Scientific Reason:

Zygotene is characterized by synapsis and formation of the synaptonemal complex, not recombination nodules.

⚠️

Student Fallacy (Why candidates pick this trap): Assuming crossing over and nodule formation happen simultaneously with pairing in zygotene.

3 3

✓ 100% Correct

Verdict & Scientific Reason:

Exact NCERT definition: appearance of recombination nodules and crossing over takes place in pachytene.

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Why this is airtight: None; textbook verbatim.

4 4

✗ Incorrect

Verdict & Scientific Reason:

Diplotene is recognized by the dissolution of the synaptonemal complex and the appearance of X-shaped chiasmata.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing visible chiasmata with recombination nodules.

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NTA Trap Alert: Zygotene vs. Pachytene Synapsis Trap

Students frequently conflate the assembly of the synaptonemal complex (zygotene) with the appearance of recombination nodules (pachytene).

🛡️ How to avoid the -1 mark: Zygotene = Synaptonemal complex forms. Pachytene = Recombination nodules appear & crossing over occurs.

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Core NEET Syllabus Standard

NCERT Biology · Cell Cycle and Cell Division Standard Benchmark

Core Scientific Principle Tested:

"Pachytene stage is characterized by the appearance of recombination nodules, the sites at which crossing over occurs between non-sister chromatids of the homologous chromosomes."

Syllabus Focus: Meiosis I - Prophase I

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

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NEET 2023 Botany Question 114 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ LZPDD Meiosis Anchor: Recombination Nodules = Pachytene

Step-by-Step Rigorous Workflow & Mathematical Proof

Chronology of Prophase I Sub-stages

Nature of Recombination Nodules

Verbatim NCERT Definition

360° Option Elimination Engine Key Feature

NTA Trap Alert: Zygotene vs. Pachytene Synapsis Trap

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

🔗 Related Questions — Cell Cycle and Cell Division

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Stages of Meiosis I and Comparison with Mitosis

Function of Spindle Fibers during Mitosis (Chromosome Segregation)

Stages of Mitosis: Spindle Fibre Attachment to Kinetochores

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