What happens during the cell cycle and mitosis, and why is it important?
Describe mitosis as part of the cell cycle, including the stages and the production of two genetically identical daughter cells, its importance in growth, repair and asexual reproduction, and cancer as uncontrolled cell division.
A focused answer to Edexcel GCSE Biology 2.1 to 2.4, covering the cell cycle and the stages of mitosis, the production of two genetically identical daughter cells, its role in growth, repair and asexual reproduction, and cancer.
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What this dot point is asking
Edexcel statements 2.1 to 2.4 want you to describe the cell cycle and the stages of mitosis, explain that mitosis makes two genetically identical daughter cells, state why mitosis matters (growth, repair and asexual reproduction), and describe cancer as the result of uncontrolled cell division.
The cell cycle
During interphase the cell grows, makes more ribosomes and mitochondria, and copies (replicates) its DNA so that each chromosome consists of two identical strands joined together. This copying is what makes it possible for both daughter cells to receive a full, identical set of genetic information.
The stages of mitosis
Edexcel names the stages: prophase, metaphase, anaphase and telophase, followed by cytokinesis.
- Prophase: the chromosomes condense and become visible, and the membrane around the nucleus breaks down.
- Metaphase: the chromosomes line up across the middle (equator) of the cell.
- Anaphase: the two strands of each chromosome are pulled apart to opposite poles of the cell.
- Telophase: a nuclear membrane forms around each new set of chromosomes.
- Cytokinesis: the cytoplasm and cell membrane divide, giving two separate daughter cells.
Why mitosis matters
Mitosis is used wherever an organism needs more identical cells:
- Growth: a fertilised egg divides again and again by mitosis to build a multicellular body.
- Repair: damaged tissues, such as a healing wound, are rebuilt with identical new cells.
- Asexual reproduction: some organisms (and plants grown from cuttings) produce genetically identical offspring (clones) entirely by mitosis.
Cancer
When the genes that control the cell cycle are damaged by mutations, a cell may divide uncontrollably instead of only when new cells are needed. The cells build up into a lump called a tumour. A benign tumour stays in one place, while a malignant (cancerous) tumour can spread to other parts of the body. So cancer is, at its root, mitosis that has lost its control.
Try this
Q1. Name the stage of the cell cycle in which DNA is copied. [1 mark]
- Cue. Interphase.
Q2. Give two processes in the body that rely on mitosis. [2 marks]
- Cue. Any two of: growth, repair of damaged tissue, replacing worn-out cells, asexual reproduction.
Exam-style practice questions
Practice questions written in the style of Pearson Edexcel exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Edexcel 20194 marksDescribe what happens during the cell cycle to produce two genetically identical daughter cells.Show worked answer →
A 4-mark describe question rewards the sequence of events in order.
- During interphase the cell grows, makes more sub-cellular structures (such as mitochondria and ribosomes) and copies its DNA, so each chromosome becomes two identical strands joined together.
- In mitosis the chromosomes line up in the middle of the cell.
- The two strands of each chromosome are pulled apart to opposite ends (poles) of the cell.
- The cytoplasm and cell membrane divide (cytokinesis), forming two daughter cells, each with an identical set of chromosomes to the parent.
Markers reward DNA replication during interphase, chromosomes lining up and separating, and two identical cells. Confusing this with meiosis (which gives four different cells) loses marks.
Edexcel 20213 marksExplain how cancer can develop from changes in cells.Show worked answer →
A 3-mark explain question rewards linking changes to uncontrolled division.
Changes (mutations) in the genes that control the cell cycle can make a cell divide uncontrollably, instead of only when new cells are needed. The cells keep dividing by mitosis, forming a mass of cells called a tumour. If the tumour spreads to other parts of the body it is a malignant (cancerous) tumour.
Markers reward the idea of changes leading to uncontrolled cell division and the formation of a tumour. Saying cancer is simply a disease, without the link to uncontrolled mitosis, scores little.
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Sources & how we know this
- Pearson Edexcel GCSE (9-1) Biology (1BI0) specification — Pearson (2016)