AQA Biology 4.6.1.2
Meiosis
One cell divides twice to make four different gametes, and two gametes make a new 46. Predict each number before it appears.
Triple Science · Higher tier
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Half from each.
People say you got your eyes from one parent and your hair from the other.
If you had to guess, does a sperm cell carry all of a parent’s chromosomes, or half?
Meiosis
Cell to embryo.
Cells in reproductive organs divide by meiosis to form gametes. Step through, from one cell to an embryo. The model shows 2 pairs of chromosomes; a human cell has 23 pairs, 46 in all.
One cell in the testes or ovaries: 46 chromosomes (23 pairs).
Fertilisation
Why halve it?
Gametes join at fertilisation to restore the normal number of chromosomes. Try it both ways.
Pick one.
Four things to remember. Tap each.
Why gametes and fertilisation matter: Sexual and asexual reproduction. What the chromosomes carry: DNA and the genome.
Think again · two cells?
“Meiosis makes two cells, like mitosis.”
Your call
ChooseHow many gametes does one cell make by meiosis?
Sort
Meiosis or mitosis?
Place each one.
Tap a card, then tap the box it belongs in. Tap a placed card to take it back.
Command words in this lesson
- Describe
- What happens when a cell divides to form gametes.
- Explain
- Why gametes have a single set of chromosomes.
- Calculate
- Chromosome numbers in gametes and after fertilisation.
Key fact
Meiosis: copies made, the cell divides twice, four gametes each with a single set of chromosomes, all genetically different. Fertilisation restores the normal number.
Key note · AQA 4.6.1.2
Meiosis
- Cells in reproductive organs divide by meiosis to form gametes.
- Copies of the genetic information are made; the cell divides twice to form four gametes, each with a single set of chromosomes.
- All gametes are genetically different. Fertilisation restores the normal number: 23 + 23 = 46.
- The new cell divides by mitosis; the number of cells increases; as the embryo develops, cells differentiate.
Photograph this card. Tomorrow, cover it and say each line first.
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Ask MrBadmus
Mixing up meiosis and mitosis?
The cells are a model, not to scale.