Sexual and asexual reproduction

Inheritance, variation and evolution · Reproduction · note 1 of 8

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Sexual and asexual reproductionSpec 4.6.1.1

In short

Sexual reproduction is the joining (fusion) of male and female gametes, such as sperm and egg cells in animals. It mixes genetic information, so the offspring show variation. Asexual reproduction involves only one parent, with no fusion of gametes and no mixing of genetic information. Only mitosis is involved, so the offspring are genetically identical to the parent (clones).

Sexual reproduction involves the joining (fusion) of male and female gametes. In animals the gametes are sperm and egg cells. In flowering plants they are pollen and egg cells.

In sexual reproduction there is mixing of genetic information, which leads to variety in the offspring. The formation of gametes involves meiosis.

Asexual reproduction involves only one parent and no fusion of gametes. There is no mixing of genetic information, so the offspring are genetically identical to the parent. Genetically identical offspring are called clones. Only mitosis is involved.

Meiosis leads to non-identical cells being formed. Mitosis leads to identical cells being formed.

Sexual and asexual reproduction compared
	Sexual reproduction	Asexual reproduction
Number of parents	Two	One
Fusion of gametes	Yes	No
Type of cell division used	Meiosis to make gametes	Mitosis only
Mixing of genetic information	Yes	No
Offspring	Genetically different from each other and from the parents	Genetically identical to the parent (clones)

Common mistake:

Do not write that asexual offspring are 'similar' to the parent. The mark is for 'genetically identical'.

Comparison of sexual reproduction, where two parents make gametes by meiosis that fuse at fertilisation to give genetically different offspring, and asexual reproduction, where one parent divides by mitosis to give a genetically identical offspring. — Sexual reproduction mixes genetic information from **two parents**; asexual reproduction makes genetically identical clones from one parent.

Written and checked against the AQA GCSE Biology (8461) specification · Updated October 2026

Frequently asked questions

Why is meiosis important for sexual reproduction?

Meiosis is important because it halves the number of chromosomes in gametes, so that fertilisation restores the full number. Human gametes have 23 chromosomes, and when an egg and a sperm join, the new cell has 46. Meiosis also makes all the gametes genetically different, which leads to variation in the offspring.

What is a genotype and phenotype?

A genotype is the alleles present for a characteristic, such as Bb, and a phenotype is how the characteristic is expressed, such as black fur. The alleles in the genotype operate at a molecular level to develop the characteristics seen in the phenotype. A black mouse could be BB or Bb, but a brown mouse must be bb.

What is a Punnett square used for in genetics?

A Punnett square is used to show the possible combinations of alleles from the gametes of two parents. Each box is equally likely, so it predicts the probability and ratio of the offspring's genotypes and phenotypes. For example, crossing two Bb mice gives a 3 : 1 ratio of black to brown, so a 25% chance of a brown mouse.

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