In-text Question
Q.What will be the ploidy of the cells of the nucellus, MMC, the functional megaspore and female gametophyte?
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Start your 14-day free trial to unlock the full solution →Nucellus and MMC are diploid (2n, ordinary sporophyte tissue); the functional megaspore and the female gametophyte it produces are both haploid (n) — the ploidy switches exactly at meiosis, and stays haploid afterward.
Tracking ploidy through the whole sequence in §1.2.2:
- Nucellus — diploid (2n). The nucellus is ordinary tissue of the ovule (the sporophyte generation), formed by normal mitotic divisions like the rest of the plant body. No meiosis has happened yet.
- Megaspore mother cell (MMC) — diploid (2n). The MMC differentiates from a nucellar cell — it is still sporophyte tissue at this point, so it is also diploid, right up until it enters meiosis.
- Functional megaspore — haploid (n). The MMC undergoes meiosis, producing four megaspores; each is haploid, since meiosis is the chromosome-halving division. Only one of these four survives (the other three degenerate) — this one surviving cell is the functional megaspore, and it is haploid. …
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