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A fern gametophyte produces gametes. Which process does it use, and why?
AMitosis, because it is already haploid
BMeiosis, because it is already haploid
CMitosis, because it is already diploid
DMeiosis, because it is already diploid
Answer & Solution
Correct answer: A. Mitosis, because it is already haploid
1. Meiosis exists to cut the number of chromosome sets from two to one.
2. A gametophyte is a multicellular plant that is already haploid.
3. It holds one chromosome set, so there is nothing left to halve.
4. Its gametes must also be haploid, matching the plant that makes them.
5. Ordinary mitosis copies a haploid cell into more haploid cells, which is exactly what is needed.
6. So the gametophyte makes gametes by mitosis, not meiosis.
7. Using meiosis here would drop the gametes below one full set, which is not viable.
8. Calling the gametophyte diploid confuses it with the sporophyte stage of the same life cycle.
_Source: OpenStax Biology 1e (CC BY 4.0), Chs 10 and 11, section 11.2 Sexual Reproduction_
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