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Meiosis

Genetics · Reproduction and meiosis · note 1 of 1

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MeiosisSpec 3.3

In short

Meiosis is the type of cell division that makes gametes. One parent cell divides to produce four daughter cells, each with half the number of chromosomes, which are genetically different from each other and from the parent cell. In humans, meiosis makes sperm and egg cells with 23 chromosomes, and fertilisation restores the full 46.

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 cells and gametes
Body cell (diploid)Gamete (haploid)
Chromosomes in a human cell4623
Genetically identical to the others?Yes, if made by mitosisNo, each gamete is different
Made byMitosisMeiosis
A diploid parent cell with 4 chromosomes divides by meiosis into four genetically different haploid gametes with 2 chromosomes each; one gamete fuses with a gamete from the other parent at fertilisation to form a diploid zygote with 4 chromosomes. (opens full size in a new tab)
Meiosis halves the chromosome number; fertilisation restores it in the zygote.
Exam tip:

The stages of meiosis are not required. Learn the outcome: four genetically different haploid gametes, each with half the number of chromosomes.

Quick check

  1. Give one advantage and one disadvantage of asexual reproduction.

    Show answer

    Advantage: no need to find a mate (or rapid reproductive cycle). Disadvantage: no variation in the population.

  2. Give one advantage and one disadvantage of sexual reproduction.

    Show answer

    Advantage: variation in the population. Disadvantage: the requirement to find a mate.

  3. How many daughter cells does one meiotic division produce?

    Show answer

    Four.

  4. How many chromosomes are in a human gamete?

    Show answer

    23, which is half the number in a body cell (46).

Written and checked against the Edexcel GCSE Combined Science (1SC0) specification · Updated October 2026

Frequently asked questions

Why is meiosis important for sexual reproduction?

Meiosis is important because it makes gametes with half the number of chromosomes of a body cell. In humans, sperm and egg cells have 23 chromosomes, so when they fuse at fertilisation the zygote has the full 46. The gametes are also genetically different, which produces variation in the offspring.

What is the difference between mitosis and meiosis?

Mitosis produces genetically identical diploid body cells. Meiosis produces four genetically different haploid gametes, each with half the number of chromosomes of the parent cell. In humans, body cells made by mitosis have 46 chromosomes, while the sperm and egg cells made by meiosis have 23, so fertilisation restores 46.

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