Q.138 Zoology ⭐ 360° Option Elimination Active

NEET 2025 Zoology Question 138 Solution

Topic: Human Reproduction · Official NTA Booklet Code 45

Question

Consider the following: A. The reductive division for the human female gametogenesis starts earlier than that of the male gametogenesis. B. The gap between the first meiotic division and the second meiotic division is much shorter for males compared to females. C. The first polar body is associated with the formation of the primary oocyte. D. Luteinizing Hormone (LH) surge leads to disintegration of the endometrium and onset of menstrual bleeding. Choose the correct answer from the options given below:

(1)A and B are true
(2)A and C are true
(3)Band D are true
(4)Band C are true

✓

Verified Against NTA Final Answer Key

Option (1) : A and B are true

📚 Human Reproduction Medium

📋 Given Parameters & Problem Setup

Statement A The reductive division for human female gametogenesis starts earlier than that of male gametogenesis.

Statement B The gap between the first meiotic division and second meiotic division is much shorter for males compared to females.

Statement C The first polar body is associated with the formation of the primary oocyte.

Statement D Luteinizing Hormone (LH) surge leads to disintegration of the endometrium and onset of menstrual bleeding.

⚡

The 30-Second Exam Hall Shortcut: ⚡ Gametogenesis Timing Diagnostic

⏱️ Save ~35 seconds

Female meiosis begins in embryonic life (foetus) vs male meiosis at puberty -> A is TRUE! Male Meiosis-I to II takes mere hours, whereas female takes decades (birth to puberty/fertilisation) -> B is TRUE! First polar body accompanies SECONDARY oocyte (C false)! LH surge triggers OVULATION, not menstruation (D false)! A and B are true!

1 Analyze each statement meticulously:

2 - Statement A: Oogenesis (reductive division / meiosis I) is initiated during the embryonic development stage before birth! Spermatogenesis begins only at puberty (13–14 years). Thus, female reductive division starts years earlier! [TRUE]

3 - Statement B: In males, secondary spermatocytes immediately undergo Meiosis II without interphase pause (gap is hours). In females, Meiosis I completes just before ovulation (puberty, 12–50 years after initiation!), and Meiosis II halts at Metaphase II until fertilization! The gap is incomparably shorter in males. [TRUE]

4 - Statement C: Meiosis I produces the SECONDARY oocyte and the first polar body (not primary oocyte). [FALSE]

5 - Statement D: LH surge induces ovulation (rupture of Graafian follicle), whereas endometrial disintegration is caused by progesterone withdrawal. [FALSE]

6 Conclusion: A and B are true!

7 Select Option (1)!

🛡️

Why You Can 100% Trust This Shortcut: Oogenesis Hormonal Milieu & Follicular Development (NCERT Biology · Human Reproduction: Primary to Graafian follicle).

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Comparative Chronology of Meiosis in Gametogenesis (Statements A & B)

Spermatogenesis and oogenesis exhibit profound temporal differences:

• Initiation: Oogenesis is initiated during the embryonic development stage when a couple of million gamete mother cells (oogonia) are formed within each foetal ovary; no more oogonia are formed and added after birth. Primary oocytes enter prophase-I of meiosis-I and get temporarily arrested. In contrast, spermatogenesis starts only at puberty due to the significant increase in the secretion of GnRH. Therefore, reductive division begins much earlier in females. Statement A is TRUE.
• Inter-meiotic Interval (Gap): In males, primary spermatocytes complete Meiosis I to form secondary spermatocytes, which immediately undergo Meiosis II to form spermatids (duration is just hours to days). In females, Meiosis I completes only at puberty inside the tertiary follicle (a gap of 12 to 50 years!), and Meiosis II is arrested at Metaphase II until sperm entry at fertilization. Hence, the gap between meiosis I and II is vastly shorter in males. Statement B is TRUE.

Step 2

Origin of Polar Bodies and Primary Oocyte (Statement C)

Cytoplasmic division during female meiosis:

• Oogonia divide mitotically to form primary oocytes (which are diploid and arrested in prophase I).
• The first meiotic division of the primary oocyte is unequal, resulting in the formation of a large haploid secondary oocyte and a tiny first polar body.
• Thus, the first polar body is associated with the formation of the secondary oocyte, NOT the primary oocyte. Statement C is FALSE.

Step 3

Physiological Action of the LH Surge (Statement D)

Hormonal events of the menstrual cycle:

• Both LH and FSH attain a peak level in the middle of the cycle (about 14th day). Rapid secretion of LH leading to its maximum level during the mid-cycle called LH surge induces rupture of Graafian follicle and thereby the release of ovum (ovulation).
• Menstrual flow and endometrial sloughing result from the degeneration of the corpus luteum and subsequent precipitous drop in progesterone levels, not from the LH surge. Statement D is FALSE.

Step 4

Conclusion

Statements A and B are true, while C and D are false. This matches Option (1).

\text{True Statements} = A \text{ and } B \text{ (Option 1)}

⭐

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 A

✓ 100% Correct

Verdict & Scientific Reason:

100% correct. Accurately verifies that female meiosis initiates earlier (fetal life) and male inter-meiotic interval is much shorter.

💡

Why this is airtight: None; exceptional mastery of human gametogenesis.

2 B

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Statement C is false because the first polar body forms alongside the secondary oocyte.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing primary oocyte with secondary oocyte.

3 C

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Statement D is false because LH surge causes ovulation, not menstrual bleeding.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing the mid-cycle ovulatory LH peak with menses.

4 D

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Incorporates false statement C and omits true statement A.

⚠️

Student Fallacy (Why candidates pick this trap): Believing primary oocytes possess polar bodies.

⚠️

NTA Trap Alert: LH Surge Function vs Menstruation Trigger

The LH surge triggers OVULATION at day 14! Menstruation occurs 14 days later (day 28) triggered by PROGESTERONE WITHDRAWAL when the corpus luteum degenerates. Never credit LH surge with endometrial sloughing!

🛡️ How to avoid the -1 mark: LH Surge = Ovulation. Progesterone Drop = Menstruation.

📖

Core NEET Syllabus Standard

NEET Biology Core Syllabus · Human Reproduction Standard Benchmark

Core Scientific Principle Tested:

"Oogenesis initiates in fetal development while spermatogenesis begins at puberty; first meiotic division produces secondary oocyte and first polar body; LH surge causes ovulation."

Syllabus Focus: Gametogenesis & Menstrual Cycle

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

A & B are biological Truth: A-Embryo start (Female), B-Brief gap (Male)!

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NEET 2025 Zoology Question 138 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Gametogenesis Timing Diagnostic

Step-by-Step Rigorous Workflow & Mathematical Proof

Comparative Chronology of Meiosis in Gametogenesis (Statements A & B)

Origin of Polar Bodies and Primary Oocyte (Statement C)

Physiological Action of the LH Surge (Statement D)

Conclusion

360° Option Elimination Engine Key Feature

NTA Trap Alert: LH Surge Function vs Menstruation Trigger

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

🔗 Related Questions — Human Reproduction

Male vs Female Accessory Ducts and Reproductive Anatomy

Endocrine Regulation of Ovulation (LH Surge) and Corpus Luteum (Progesterone)

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Secondary Oocyte Envelopes (Zona Pellucida vs Corona Radiata)

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