Meiosis
Biology: AQA GCSE Higher, topic 6.1.2
Meiosis and Mitosis
Sexual reproduction is the fusion (joining together) of male and female gametes. Cells in reproductive organs divide by meiosis to create gametes. Gametes contain half of the number of chromosomes (containing DNA) found in all body cells.
Cells split
- Each cell has a pair of each chromosome (diploid cell).
- During meiosis each pair of chromosomes replicate and the cell splits in two.
Further cell splitting
- There are now two identical cells.
- The diploid cell divides again.
Haploid cells created
- This creates four genetically different gametes that each have half the number of chromosomes that are found in the parent cell.
- Cells that have only one copy of each chromosome (such as gametes) are called haploid cells.
Gametes fertilise
- During sexual reproduction, the male gamete fertilises the female gamete and the fertilised cell now has the normal number of chromosomes (46 in humans).
Mitosis
- Once the gametes have combined, the new cell divides by mitosis (the cell grows asexually).
- As soon as the embryo reaches a certain size, cells begin to differentiate (specialise).
Test yourself on Meiosis
Meiosis
What are the four genetically different gametes produced during meiosis called?
What happens to the number of chromosomes when a male gamete fertilises a female gamete?
Why does the fertilised cell have the normal number of chromosomes for the species?
A diploid cell contains a pair of each chromosome. Why are gametes classed as haploid cells instead of diploid cells?