AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Sexual and asexual reproduction: Students should understand that meiosis leads to non-identical cells being formed while mitosis leads to identical cells being formed.
Mitosis and meiosis both copy DNA before dividing, but they differ in outcome.
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Mitosis and meiosis both copy DNA before dividing, but they differ in outcome. In mitosis one parent cell divides once to give two daughter cells that are genetically identical to each other and to the parent, so chromosome number is unchanged; this suits growth, repair and asexual reproduction. In meiosis a cell divides twice to give four gametes. Because pairs of chromosomes separate and genetic information is mixed, each gamete is genetically different from the parent and from the other gametes. Fertilisation then restores the full number of chromosomes, so sexual reproduction produces non-identical offspring.
What earns the marks
- Mitosis involves one division and produces two daughter cells that are genetically identical to the parent cell, with the same chromosome number.
- Meiosis involves two divisions and produces four gametes, each with half the chromosome number of the parent cell.
- In meiosis, pairs of chromosomes separate and genetic information is mixed, so the resulting cells are non-identical.
- Mitosis supports growth, repair of tissues and asexual reproduction, where identical offspring are advantageous.
- Meiosis produces gametes for sexual reproduction, and the genetic variation it generates gives offspring a better chance of surviving changed conditions.
Common mistakes and how to put them right
Saying meiosis produces two cells.
Put it right by stating that meiosis involves two divisions and produces four gametes.
Saying mitosis produces gametes.
Put it right by stating that mitosis produces identical body cells for growth and repair, while meiosis produces gametes.
Believing meiosis keeps the chromosome number the same.
Put it right by stating that meiosis halves the chromosome number.
Exam tips
- State the number of divisions and the number and type of cells produced for each process before explaining the genetic outcome.
- Use the terms diploid and haploid to compare chromosome numbers in parent cells, gametes and daughter cells.
- When comparing the two processes, structure your answer as direct pairs, such as one division versus two divisions, rather than describing each process separately.
Try the lesson
The start of the Sexual and asexual reproduction: Students should understand that meiosis leads to non-identical cells being formed while mitosis leads to identical cells being formed. lesson, made from checked teaching notes for this specification point.
Have a go first
Which type of cell division produces genetically identical cells?
Listen
Mitosis and meiosis both copy DNA before dividing, but they differ in outcome. In mitosis one parent cell divides once to give two daughter cells that are genetically identical to each other and to the parent, so chromosome number is unchanged; this suits growth, repair and asexual reproduction. In meiosis a cell divides twice to give four gametes. Because pairs of chromosomes separate and genetic information is mixed, each gamete is genetically different from the parent and from the other gametes. Fertilisation then restores the full number of chromosomes, so sexual reproduction produces non-identical offspring. A strong answer earns marks for these points. Mitosis involves one division and produces two daughter cells that are genetically identical to the parent cell, with the same chromosome number. Meiosis involves two divisions and produces four gametes, each with half the chromosome number of the parent cell. In meiosis, pairs of chromosomes separate and genetic information is mixed, so the resulting cells are non-identical. Mitosis supports growth, repair of tissues and asexual reproduction, where identical offspring are advantageous. A common slip: Saying meiosis produces two cells. Instead, stating that meiosis involves two divisions and produces four gametes. Exam tip: State the number of divisions and the number and type of cells produced for each process before explaining the genetic outcome.
See it
Key words
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Mitosis
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Meiosis
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Fertilisation
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Gametes
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See every definition
- Mitosis
- One parent cell divides once to give two daughter cells that are genetically identical to each other and to the parent, so chromosome number is unchanged.
- Meiosis
- A cell divides twice to give four gametes, each genetically different from the parent and from the other gametes.
- Fertilisation
- Restores the full number of chromosomes, so sexual reproduction produces non-identical offspring.
- Gametes
- Cells produced by meiosis, each with half the chromosome number of the parent cell.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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