AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Genetic inheritance: gamete
A gamete is a sex cell produced by meiosis.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 2 of 20
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A gamete is a sex cell produced by meiosis. In humans, the gametes are sperm and egg cells; in flowering plants, they are pollen and egg cells. Each gamete is haploid, meaning it contains one chromosome from each homologous pair, so it carries one allele of each gene. At fertilisation, two gametes fuse to form a diploid zygote, restoring the full chromosome number and creating new allele combinations. For example, a human sperm carries 23 chromosomes and an egg carries 23; their fusion gives a zygote with 46 chromosomes. This explains why offspring inherit one allele from each parent and why gametes are central to genetic variation.
What earns the marks
- Define a gamete as a sex cell, such as sperm, egg or pollen, involved in sexual reproduction.
- State that gametes are haploid, containing one set of chromosomes, for example 23 in human gametes.
- Explain that gametes carry one allele from each gene pair because they are produced by meiosis.
- Describe fertilisation as the fusion of two gametes to form a diploid zygote with two sets of chromosomes.
- Link gamete formation to genetic variation: meiosis and random fertilisation produce new allele combinations.
- Compare gametes with body cells, which are diploid and contain two sets of chromosomes.
Common mistakes and how to put them right
Saying gametes are diploid.
Put it right: Gametes are haploid, so they contain one set of chromosomes, not two.
Confusing gametes with body cells.
Put it right: Body cells are diploid and carry two alleles of each gene, while gametes carry one.
Thinking gametes are produced by mitosis.
Put it right: Gametes are produced by meiosis, which halves the chromosome number.
Writing that fertilisation produces a gamete.
Put it right: Fertilisation joins two gametes to form a zygote.
Exam tips
- Quote the haploid number for humans (23) and the diploid number (46) to show precise knowledge.
- When explaining inheritance, show gametes as single letters in a Punnett square, for example T or t, not TT or Tt.
- Use the term zygote for the cell formed at fertilisation and state that it is diploid.
- Link gametes to variation by mentioning meiosis and the random fusion of gametes.
Try the lesson
The start of the Genetic inheritance: gamete lesson, made from checked teaching notes for this specification point.
Have a go first
What is a gamete? Select the correct answer.
Listen
A gamete is a sex cell produced by meiosis. In humans, the gametes are sperm and egg cells; in flowering plants, they are pollen and egg cells. Each gamete is haploid, meaning it contains one chromosome from each homologous pair, so it carries one allele of each gene. At fertilisation, two gametes fuse to form a diploid zygote, restoring the full chromosome number and creating new allele combinations. For example, a human sperm carries 23 chromosomes and an egg carries 23; their fusion gives a zygote with 46 chromosomes. This explains why offspring inherit one allele from each parent and why gametes are central to genetic variation. A strong answer earns marks for these points. Define a gamete as a sex cell, such as sperm, egg or pollen, involved in sexual reproduction. State that gametes are haploid, containing one set of chromosomes, for example 23 in human gametes. Explain that gametes carry one allele from each gene pair because they are produced by meiosis. Describe fertilisation as the fusion of two gametes to form a diploid zygote with two sets of chromosomes. Exam tip: Quote the haploid number for humans (23) and the diploid number (46) to show precise knowledge.
See it
Key words
Say what each word means before you turn the card.
Gamete
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Haploid
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Fertilisation
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Zygote
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See every definition
- Gamete
- A sex cell produced by meiosis, such as sperm and egg cells in humans or pollen and egg cells in flowering plants.
- Haploid
- Containing one chromosome from each homologous pair, so carrying one allele of each gene.
- Fertilisation
- The fusion of two gametes to form a diploid zygote, restoring the full chromosome number and creating new allele combinations.
- Zygote
- The diploid cell formed at fertilisation when two gametes fuse, restoring the full chromosome number.
Label the diagram
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1Box 1
2Box 2
3Box 3
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