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NDA Biology · Reproduction

Meiosis in Flowering Plants — Where the DNA Halves

In a flowering plant the diploid DNA content is halved by meiosis during gamete formation — specifically when pollen (the male gamete) and the egg are made, not during seed germination, fruit formation, or bud formation.

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Why this matters

A single but sharp PYQ (2023, MODERATE) that tests one idea: meiosis — and therefore the halving of DNA — happens at GAMETE FORMATION, before fertilisation, not at any later stage of the plant's life. It is the plant-specific version of the ploidy reasoning from the previous subtopic.

Concept 1 of 1: DNA is halved during pollen (gamete) formation

Walk the timeline of a flowering plant. The plant is diploid (2n). To make gametes it does meiosis, which halves the DNA to haploid (n) — this happens when POLLEN forms in the anther and when the egg forms in the ovule. Fertilisation then restores 2n. So the only moment the DNA drops to half is gamete formation. Everything after fertilisation (seed, fruit, germination) is already back to 2n.

Definition

In flowering plants, the parent's DNA content is halved by meiosis during gamete (pollen and egg) formation:

  • Pollen formation (microsporogenesis, in the anther) — meiosis halves DNA → haploid pollen. This is the answer.
  • Seed germination — the embryo is already diploid (2n); no halving.
  • Fruit formation — the ovary (2n) develops into fruit after fertilisation; no halving.
  • Flower bud formation — ordinary growth by mitosis, which keeps the DNA content the same.

Halving happens once, at gamete formation, BEFORE fertilisation.

Worked example

At which stage of a flowering plant's life is the DNA content reduced to half: when the anther makes pollen, when a flower bud grows, when a fruit ripens, or when a seed germinates?
Practice this concept3 quick reps

The same idea in a real exam question:

NDA · Sep 2023 · Q94Moderate

Example 1 · Reproduction · Meiosis and DNA in Flowering Plants

In flowering plants, DNA content of the parent plant gets halved during

Halving = gamete formation, not germination or fruiting

The distractors (seed germination, fruit formation, flower bud formation) all occur by mitosis or after fertilisation — they keep the DNA at 2n. Only pollen/gamete formation uses meiosis and halves the DNA.

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