Cell Division: Mitosis and the Cell Cycle — AQA GCSE Biology
Body cells divide by mitosis for growth, repair and replacement. This topic covers the cell cycle and the role of mitosis.
The cell cycle
The cell cycle is the series of stages a cell goes through to divide. It has three main parts:
- Growth and DNA replication (interphase) — the cell grows, makes more sub-cellular structures (ribosomes and mitochondria), and copies its DNA so each chromosome becomes two identical copies joined together.
- Mitosis — one set of chromosomes is pulled to each end of the cell, and the nucleus divides.
- Division of the cytoplasm and cell membrane — two genetically identical daughter cells form.
Chromosomes
The genetic material is stored in chromosomes, found in the nucleus. Body cells normally have two copies of each chromosome (one from each parent). In humans, body cells have 23 pairs (46 chromosomes).
Why mitosis matters
Mitosis produces two genetically identical daughter cells. It is essential for:
- Growth of an organism.
- Repair of damaged tissue and replacement of worn-out cells.
- Asexual reproduction in some organisms.
Exam tips
- Remember mitosis produces two genetically identical cells.
- Know the order: DNA is copied first, then chromosomes separate, then the cell divides.
- Mitosis is for growth, repair and asexual reproduction — don't confuse it with meiosis (which makes gametes).
- The DNA replicates before the cell divides, so each new cell gets a full set.