Q56. Match the cell/tissue types in GROUP I with their corresponding total DNA
content in GROUP II of a typical diploid Angiosperm species and choose
the CORRECT option (C denotes DNA content in haploid genome).
| GROUP I | GROUP II |
| (P) Pollen tube | (1) C |
| (Q) Megaspore mother cell | (2) 2C |
| (R) Synergid prior to fertilization | (3) 4C |
| (S) Embryo prior to fertilization | (5) 8C |
| (A) P-1, Q-2, R-3, S-5 |
| (B) P-2, Q-2, R-1, S-5 |
| (C) P-1, Q-2, R-1, S-5 |
| (D) P-2, Q-1, R-2, S-4 |
The correct matching for tissue types and DNA content in a typical diploid angiosperm is option (A): P1-Q2-R3-S5.
This pairing aligns pollen tube (1C), megaspore mother cell (4C), synergid prior to fertilization (1C), and embryo sac (1C) with their respective DNA levels based on standard ploidy in angiosperm reproduction.
Tissue Explanations
Pollen tube nuclei, including the two sperm cells, maintain 1C haploid DNA content after mitotic division from the generative cell.
Megaspore mother cell, a diploid sporocyte in G2 phase before meiosis, holds 4C DNA due to replication.
Synergids, derived from haploid megaspore mitoses in the Polygonum-type embryo sac, contain 1C DNA before fertilization.
Embryo sac cells (egg, synergids, antipodals) are haploid at 1C prior to fertilization; the central cell has two 1C polar nuclei (sometimes fusing to 2C).
Option Analysis
Option (A) P1-Q2-R3-S5: Correct, as it matches 1C pollen tube, 4C megaspore mother cell, 1C synergid, 1C embryo sac.
Option (B) P2-Q2-R1-S5: Incorrect; pollen tube is not 2C (vegetative nucleus may vary, but sperms are 1C), synergid not 1C misplaced.
Option (C) P1-Q2-R1-S5: Wrong; synergid matches 3C? No, it’s 1C, not 3C.
Option (D) P2-Q1-R2-S4: Flawed; pollen tube not 2C primary, megaspore mother not 2C, synergid not 2C, embryo sac not 3C pre-fertilization.
In typical diploid angiosperms, matching DNA content (C-values denoting haploid genome) across reproductive tissues is crucial for CSIR NET Life Sciences preparation. This guide breaks down pollen tube, megaspore mother cell, synergid prior to fertilization, and embryo sac ploidy with precise explanations.
Key Concepts in Angiosperm Reproduction
Angiosperm sporophyte is diploid (2C in G1). Meiosis produces haploid (1C) gametophytes; DNA replication yields 2C/4C pre-division.
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Pollen Tube: Carries two 1C sperm nuclei post-mitosis from 2C generative cell.
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Megaspore Mother Cell: 2C sporocyte replicates to 4C before meiosis I.
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Synergid (Pre-Fertilization): Haploid cell in embryo sac, 1C DNA.
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Embryo Sac: 7-celled, 8-nucleate structure; most cells 1C haploid.
Detailed DNA Content Breakdown
| Tissue | DNA Content | Ploidy/Stage | Notes |
|---|---|---|---|
| Pollen Tube | 1C | Haploid sperms | Post-mitotic division |
| Megaspore Mother Cell | 4C | Diploid G2 | Pre-meiosis replication |
| Synergid Prior Fertilization | 1C | Haploid | From mitotic divisions |
| Embryo Sac | 1C | Haploid cells | Polygonum type standard |
This table clarifies matches: Group I (P=1C, Q=4C, R=1C, S=1C) pairs with Group II (1,2,3,5).
CSIR NET Exam Strategies
Focus on G1 vs G2 DNA levels and pre/post-fertilization changes (e.g., endosperm becomes 3C post). Practice similar matching questions for accuracy.
