AQA GCSE Combined Science Foundation (8464), Foundation tier · Biology › Inheritance, variation and evolution › Reproduction
Practise Meiosis. 9 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
Meiosis is the cell division that makes gametes with a single set of chromosomes; fertilisation then restores the full number. Expect questions describing meiosis, comparing it with mitosis and explaining why gametes must have half the number of chromosomes.
Key facts
Meiosis happens in the reproductive organs and makes gametes
Genetic information copied → cell divides twice → four gametes
Each gamete has a single set of chromosomes; all gametes are genetically different
Human body cell: 46 chromosomes (23 pairs). Human gamete: 23 chromosomes
Fertilisation restores the normal number of chromosomes
After fertilisation: mitosis → more cells → cells differentiate as the embryo develops
Meiosis is a type of cell division that happens in the reproductive organs (e.g. the testes and ovaries in humans) to make gametes.
First, copies of the genetic information are made.
The cell then divides twice, forming four gametes.
Each gamete has a single set of chromosomes (half the normal number). A human body cell has 46 chromosomes (23 pairs); a human gamete has 23.
All the gametes are genetically different from each other.
Meiosis in humans: copy, then divide twice, giving four gametes with 23 chromosomes each.
You do not need to know the stages of meiosis.
Fertilisation and development
diagram
At fertilisation a male gamete and a female gamete join. Each brings one set of chromosomes, so the normal number of chromosomes is restored (23 + 23 = 46 in humans).
Fertilisation restores the normal number: 23 + 23 = 46.
If gametes had the full number of chromosomes, the number would double in every generation.
The new cell divides by mitosis, so the number of cells increases.
As the embryo develops, the cells differentiate (become specialised).
Meiosis compared with mitosis
Mitosis: one division, two cells, full number of chromosomes (in pairs), cells genetically identical. Used for growth, repair and asexual reproduction.
Meiosis: two divisions, four cells, a single set of chromosomes, cells genetically different. Used to make gametes.
How to answer each type of question
Describe how gametes are formed
3 marksGrade 5
Start with copying the genetic information.
Say the cell divides twice to make four gametes.
Finish with: each gamete has a single set of chromosomes and all are genetically different.
Example. Describe how a cell in a testis divides to form sperm cells. [3 marks]
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Copies of the genetic information are made (1). The cell divides twice to form four gametes (1). Each gamete has a single set of chromosomes / half the number of chromosomes, and the gametes are all genetically different (1).
Example. A body cell of a dog contains 78 chromosomes. (a) How many chromosomes are in a dog sperm cell? (b) How many chromosomes are in a fertilised dog egg cell? [2 marks]
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(a) 78 ÷ 2 = 39 (1) (b) 39 + 39 = 78 (1)
Don’t lose marks
Saying meiosis divides once or makes two cells. It divides twice and makes four gametes.
Saying a human gamete has 23 pairs of chromosomes. It has 23 single chromosomes; body cells have 23 pairs.
Saying the embryo grows by meiosis. After fertilisation, cells divide by mitosis.
Forgetting that the genetic information is copied before the cell divides.
Writing 'the gametes are different' without saying 'genetically different'.
More tips
Memory tricks
Mitosis is '1, 2, same': 1 division, 2 cells, genetically identical. Meiosis is '2, 4, different'.
Gametes are 'half' cells: halve the body cell number to get the gamete number, and double it back at fertilisation.
Meiosis happens only in the reproductive organs. If the question is about growth or repair, the answer is mitosis.
Exam technique
For 'why do gametes have half' questions, the key idea is that fertilisation restores the normal number of chromosomes.
In compare questions, give matched pairs of facts (meiosis ... whereas mitosis ...).
Talk about the number of chromosomes halving, not the number of 'genes' or 'cells'.
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
State where and why meiosis happensCells in the reproductive organs divide by meiosis to form gametes.
Grade 4
State how many gametes meiosis producesThe cell divides twice to form four gametes.
Grade 5
Describe what happens in meiosisThe genetic information is copied, then the cell divides twice to give four genetically different gametes, each with a single set of chromosomes.
Grade 5
Give chromosome numbers in body cells and gametesA human body cell has 46 chromosomes (23 pairs) and a human gamete has 23.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
Human body cells contain 46 chromosomes. How many chromosomes are there in a human sperm cell?
23
State one similarity between mitosis and meiosis in what happens to the DNA before either type of division begins.
The DNA (genetic information) is copied before the cell divides, in both types of division
The stages below, involving cell division, happen during human reproduction, but they are in the wrong order. A Mitosis produces the millions of cells of a growing embryo. B Meiosis in the ovaries and testes produces gametes (eggs and sperm). C Fertilisation restores the full number of chromosomes. D The fertilised egg (zygote) begins to divide. Write the letters in the correct order.
B, C, D, A
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
Gametes are produced by a type of cell division called meiosis.
(a) Where does meiosis take place in the human body? Tick (✓) one box.[1]
In the brain
In the ovaries and testes
In the skin
In the stomach
(b) How many cells are produced when one cell divides by meiosis? Tick (✓) one box.[1]
1
2
4
8
(c) Human body cells contain 46 chromosomes. How many chromosomes are there in a human sperm cell?[1]
(d) After fertilisation, the fertilised egg divides many times to form an embryo. Name the type of cell division involved.[1]
Show the answer and mark scheme
(a)Answer: In the ovaries and testes
(b)Answer: 4
(c)Answer: 23
23
(d)Answer: Mitosis
mitosis
Question 2Medium7 marks
Cells in reproductive organs divide by meiosis to form gametes.
(a) Describe what happens when a cell divides by meiosis.[3]
(b) Explain why it is important that gametes contain half the number of chromosomes of a body cell.[2]
(c) Describe what happens to the fertilised egg as it develops into an embryo.[2]
Show the answer and mark scheme
(a)Answer: Copies of the genetic information are made; the cell divides twice to form four gametes, each with a single set of chromosomes; the gametes are all genetically different
copies of the genetic information / chromosomes are made
the cell divides twice
four gametes are formed, each with a single set of chromosomes / half the number of chromosomes
the gametes are all genetically different from each other
(b)Answer: When two gametes join at fertilisation the normal number of chromosomes is restored; otherwise the number would double every generation
(so that) when gametes join at fertilisation the normal / full number of chromosomes is restored
otherwise the chromosome number would double in each generation
(c)Answer: It divides by mitosis so the number of cells increases, and the cells differentiate as the embryo develops
divides by mitosis / the number of cells increases