Q.129 Botany ⭐ 360° Option Elimination Active

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NEET 2023 Botany Question 129 Solution

Topic: Sexual Reproduction in Flowering Plants · Official NTA Booklet Code G5

Question

In angiosperm, the haploid, diploid and triploid structures of a fertilized embryo sac sequentially are:

(1)Synergids, antipodals and Polar nuclei
(2)Synergids, Primary endosperm nucleus and zygote
(3)Antipodals, synergids, and primary endosperm nucleus
(4)Synergids, Zygote and Primary endosperm nucleus

✓

Verified Against NTA Final Answer Key

Option (4) : Synergids, Zygote and Primary endosperm nucleus

📚 Sexual Reproduction in Flowering Plants Easy

📋 Given Parameters & Problem Setup

Organism Angiosperms

Ploidy Sequence Haploid (

n

), Diploid (

2n

), and Triploid (

3n

)

⚡

The 30-Second Exam Hall Shortcut: ⚡ Sequential Ploidy Check: n → 2n → 3n

⏱️ Save ~20 seconds

Match the ploidy levels sequentially: Haploid ( $n$ ) = Synergid / Antipodal; Diploid ( $2n$ ) = Zygote (from syngamy $n+n$ ); Triploid ( $3n$ ) = Primary Endosperm Nucleus / PEN (from triple fusion $2n+n$ )! Match Option (4)!

1 Identify Haploid (

n

): Synergids, Antipodals, Egg cell, Male gametes.

2 Identify Diploid (

2n

): Zygote (

n \text{ egg} + n \text{ sperm}

), secondary nucleus before fertilization.

3 Identify Triploid (

3n

): Primary Endosperm Nucleus (

2n \text{ central cell} + n \text{ sperm}

4 Check Sequence: Synergids (

n

) -> Zygote (

2n

) -> PEN (

3n

5 Match Option (4).

🛡️

Why You Can 100% Trust This Shortcut: Canonical NCERT Angiosperm double fertilization and embryo sac cytology.

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Cytological Status of Embryo Sac Cells

Analyzing the ploidy of cells present in a fertilized angiosperm embryo sac following double fertilization:

\begin{aligned} \text{\textbf{Haploid (}} n \textbf{):} & \quad \text{Synergids, Antipodals (cells of the gametophyte)} \\[4pt] \text{\textbf{Diploid (}} 2n \textbf{):} & \quad \text{Zygote } (n_{\text{egg}} + n_{\text{sperm}} \text{ via Syngamy}) \\[4pt] \text{\textbf{Triploid (}} 3n \textbf{):} & \quad \text{Primary Endosperm Nucleus/PEN } (2n_{\text{polar nuclei}} + n_{\text{sperm}} \text{ via Triple Fusion}) \end{aligned}

Step 2

Matching the Specified Sequence

The question specifically requires the sequence: haploid ( $n$ ), diploid ( $2n$ ), and triploid ( $3n$ ):

\mathbf{n \longrightarrow 2n \longrightarrow 3n} \iff \mathbf{\text{Synergids } (n) \longrightarrow \text{Zygote } (2n) \longrightarrow \text{PEN } (3n)}

Step 3

Evaluation of Distractor Options

Option (1) lists synergids ( $n$ ), antipodals ( $n$ ), polar nuclei ( $n+n$ ). Option (2) lists synergids ( $n$ ), PEN ( $3n$ ), zygote ( $2n$ )—violating sequential order. Option (3) lists antipodals ( $n$ ), synergids ( $n$ ), PEN ( $3n$ ). Only Option (4) strictly adheres to the requested $n \to 2n \to 3n$ sequence.

⭐

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:

Synergids and antipodals are both haploid ( $n$ ); lacks a diploid ( $2n$ ) and triploid ( $3n$ ) structure.

⚠️

Student Fallacy (Why candidates pick this trap): Failing to track sequential ploidy values.

2 2

✗ Incorrect

Verdict & Scientific Reason:

The sequence is $n \to 3n \to 2n$ , which violates the required $n \to 2n \to 3n$ sequence.

⚠️

Student Fallacy (Why candidates pick this trap): Overlooking that triploid PEN is placed before diploid zygote.

3 3

✗ Incorrect

Verdict & Scientific Reason:

Antipodals and synergids are both haploid ( $n$ ); no diploid structure is represented.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing two haploid cells with a diploid structure.

4 4

✓ 100% Correct

Verdict & Scientific Reason:

Strictly satisfies the $n \to 2n \to 3n$ sequence: Synergids ( $n$ ), Zygote ( $2n$ ), Primary endosperm nucleus ( $3n$ ).

💡

Why this is airtight: None; rigorous sequence matching.

⚠️

NTA Trap Alert: Order of Words in Sequential Prompts Trap

Students readily know the ploidy of individual cells, but fail to notice that Option (2) switches the order to $n \to 3n \to 2n$ .

🛡️ How to avoid the -1 mark: Write down "n, 2n, 3n" on scratch paper and match the exact sequence term-by-term.

📖

Core NEET Syllabus Standard

NCERT Biology · Sexual Reproduction in Flowering Plants Standard Benchmark

Core Scientific Principle Tested:

"Syngamy results in the formation of a diploid zygote (2n), while triple fusion produces a triploid primary endosperm nucleus (3n). Synergids remain haploid (n)."

Syllabus Focus: Double Fertilisation

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

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NEET 2023 Botany Question 129 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Sequential Ploidy Check: n → 2n → 3n

Step-by-Step Rigorous Workflow & Mathematical Proof

Cytological Status of Embryo Sac Cells

Matching the Specified Sequence

Evaluation of Distractor Options

360° Option Elimination Engine Key Feature

NTA Trap Alert: Order of Words in Sequential Prompts Trap

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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