Meiosis
Introduced| English | Meaning |
|---|---|
| gametes/ˈɡæmiːts/ | Haploid reproductive cells that fuse during fertilisation to form a zygote. |
| meiosis/meɪˈəʊsɪs/ | A type of nuclear division that produces haploid nuclei with half the original chromosome number and creates genetic variation. |
| variation/ˌveərɪˈeɪʃn/ | Differences in characteristics between individuals or values within a set. |
Making gametes 配子
- Gametes must carry only half the chromosomes, so that fertilisation restores the full set.
- The special division that does this is meiosis 减数分裂.
Meiosis produces how many cells from one parent cell?
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Meiosis makes four gametes.
Each cell made by meiosis has:
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Gametes carry half the chromosomes.
Meiosis produces the sex cells, also called ______.
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Gametes have half the chromosome number.
What meiosis is
- Meiosis produces four cells, each with half the chromosome number.
- These cells are the gametes (sperm and eggs).
A Punnett square for Bb x Bb gives a 3:1 ratio of dominant to recessive
Meiosis
Meiosis makes gametes — four cells, each with HALF the chromosomes and all different.
Meiosis is important because it:
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Meiosis mixes genes, producing variation.
It creates variation 变异
- Meiosis mixes the genes, so each gamete is genetically different.
- This is a major source of variation in sexual reproduction.
Halving the chromosome number stops it doubling each generation.
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Fertilisation then restores the full number.
Mitosis vs meiosis
- Mitosis: 2 identical cells, full chromosome number — growth/repair.
- Meiosis: 4 varied cells, half the number — making gametes.
Meiosis halves the chromosome number; mitosis keeps it the same. This halving is essential — without it, the chromosome number would double every generation at fertilisation.
You've got it
- meiosis makes four cells, each with half the chromosome number — the gametes
- it mixes genes, creating variation
- mitosis = 2 identical (full number); meiosis = 4 varied (half number)
Write from four gametes
- A cell in the ovary divides to make sex cells.
- Four new cells are produced.
Which division is this, and how does the chromosome number compare with the parent cell?
Halving lets fertilisation restore the full set.
How many cells does meiosis make, and what is special about their chromosomes?
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Meiosis makes four varied gametes.