MeiosisSpec 3.3
Meiotic cell division (meiosis) is the type of cell division that makes gametes. In humans it happens in the reproductive organs.
- One parent cell divides to produce four daughter cells.
- Each daughter cell has half the number of chromosomes of the parent cell.
- The daughter cells are genetically different from each other and from the parent cell.
- The daughter cells are haploid gametes, with one set of chromosomes.
A human body cell has 46 chromosomes. Meiosis makes sperm and egg cells with 23 chromosomes each. At fertilisation the two gametes fuse and the zygote has 46 chromosomes again, with half from each parent.
| Body cell (diploid) | Gamete (haploid) | |
|---|---|---|
| Chromosomes in a human cell | 46 | 23 |
| Genetically identical to the others? | Yes, if made by mitosis | No, each gamete is different |
| Made by | Mitosis | Meiosis |
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Give one advantage and one disadvantage of asexual reproduction.
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Advantage: no need to find a mate (or rapid reproductive cycle). Disadvantage: no variation in the population.
Give one advantage and one disadvantage of sexual reproduction.
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Advantage: variation in the population. Disadvantage: the requirement to find a mate.
How many daughter cells does one meiotic division produce?
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Four.
How many chromosomes are in a human gamete?
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23, which is half the number in a body cell (46).