Meiosis
Practise Meiosis for GCSE Biology with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. Meiosis produces four genetically different gametes, each with half the normal number of chromosomes.
Free downloads
These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
Topic overview
Meiosis is the type of cell division that produces gametes. It halves the chromosome number and produces four genetically different cells.
It happens in the reproductive organs. The chromosomes are copied, then the cell divides twice to form four gametes, each with a single set of chromosomes and each genetically different from the others.
At fertilisation, two gametes fuse to restore the normal chromosome number. The new cell then divides by mitosis, and as the embryo develops the cells differentiate into specialised types. The contrast with mitosis — two identical cells versus four different ones — is examined constantly.
Revision notes
The process
Meiosis occurs in the reproductive organs. Copies of the genetic information are made first.
The cell then divides twice to form four gametes, each with a single set of chromosomes — half the number in a body cell. All four are genetically different from one another.
Fertilisation and after
At fertilisation, a male and a female gamete fuse, restoring the normal number of chromosomes.
The new cell divides by mitosis, and the number of cells increases. As the embryo develops, cells differentiate into different types.
Mitosis versus meiosis
Mitosis: two cells, genetically identical, same chromosome number, used for growth and repair.
Meiosis: four cells, genetically different, half the chromosome number, used to make gametes. Being able to state all four contrasts is worth several marks.
Key points
- Meiosis produces gametes.
- It occurs in the reproductive organs.
- The cell divides twice, producing four cells.
- Each gamete has half the chromosome number.
- All four gametes are genetically different.
- Fertilisation restores the normal chromosome number.
Worked examples
Example 1
State two differences between mitosis and meiosis. [2 marks]
Model answer
Mitosis produces two cells, whereas meiosis produces four (1 mark). Mitosis produces genetically identical cells with the full chromosome number, whereas meiosis produces genetically different cells with half the chromosome number (1 mark).
Example 2
Explain why gametes must contain half the number of chromosomes found in a body cell. [2 marks]
Model answer
At fertilisation two gametes fuse (1 mark), so if each contains half the number, the resulting cell has the normal full number rather than double it (1 mark).
Example 3
Describe what happens to the cell formed at fertilisation. [3 marks]
Model answer
It divides by mitosis (1 mark), and the number of cells increases as the embryo develops (1 mark). As the embryo grows, the cells differentiate to become specialised for particular functions (1 mark).
Common mistakes
Saying meiosis produces two cells.
It produces four. Mitosis produces two.
Saying meiosis happens throughout the body.
It occurs only in the reproductive organs.
Saying meiotic cells are identical.
All four are genetically different, which is a source of variation.
Confusing the number of divisions.
Meiosis involves two divisions; mitosis involves one.
Exam tips
- Learn the four mitosis-versus-meiosis contrasts as a set.
- Explain the halving by referring to fertilisation.
- Say genetically different, not just different.
- Name the reproductive organs as the site of meiosis.
Key terms
- Meiosis
- Cell division producing four genetically different gametes.
- Gamete
- A sex cell with half the usual chromosome number.
- Fertilisation
- The fusion of two gametes restoring the chromosome number.
- Embryo
- The early stage of development after fertilisation.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.