Mitosis and the Cell Cycle
Master Mitosis and the Cell Cycle for GCSE Biology with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. Learn the cell cycle in order: cell growth and DNA replication, then mitosis, then division of the cytoplasm and membranes to form two identical cells.
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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
Topic overview
Mitosis is the stage of the cell cycle in which the nucleus divides to produce two genetically identical cells. It is used for growth, repair and replacement.
The cell cycle has three stages. First the cell grows and increases the number of sub-cellular structures such as ribosomes and mitochondria, and the DNA replicates so each chromosome forms an identical copy joined to it.
Then mitosis occurs: one set of chromosomes is pulled to each end of the cell and the nucleus divides. Finally the cytoplasm and cell membrane divide to form two identical daughter cells, each with the same number of chromosomes as the original.
Revision notes
Stage 1: growth and DNA replication
The cell grows, and the number of sub-cellular structures such as ribosomes and mitochondria increases.
The DNA replicates, so each chromosome produces an exact copy of itself. This is why the daughter cells end up genetically identical.
Stage 2: mitosis
One set of chromosomes is pulled to each end of the cell, and the nucleus divides into two.
This is the stage that gives the process its name, but it is only one part of the whole cell cycle.
Stage 3: cytokinesis and the purpose
The cytoplasm and cell membrane divide, producing two genetically identical daughter cells.
Mitosis is used for growth, repair of damaged tissue, and replacement of worn-out cells. In some organisms it is also the basis of asexual reproduction.
Key points
- Mitosis produces two genetically identical daughter cells.
- It is used for growth, repair and replacement.
- DNA replicates before the nucleus divides.
- Each daughter cell has the same number of chromosomes as the parent.
- The cell cycle is growth, then mitosis, then division of the cytoplasm.
- Mitosis is the basis of asexual reproduction.
Worked examples
Example 1
State two purposes of mitosis in a multicellular organism. [2 marks]
Model answer
Growth of the organism (1 mark) and repair or replacement of damaged or worn-out cells (1 mark).
Example 2
Explain why the cells produced by mitosis are genetically identical. [2 marks]
Model answer
The DNA replicates before the nucleus divides, so each chromosome produces an exact copy of itself (1 mark). One complete set of chromosomes is then pulled to each end of the cell, so each daughter cell receives identical genetic information (1 mark).
Example 3
Describe what happens during the cell cycle before the nucleus divides. [3 marks]
Model answer
The cell grows (1 mark) and the number of sub-cellular structures such as ribosomes and mitochondria increases (1 mark). The DNA replicates so that each chromosome forms an identical copy (1 mark).
Common mistakes
Saying mitosis produces four cells.
Mitosis produces two identical cells. Four non-identical cells come from meiosis.
Saying the daughter cells have half the chromosomes.
That is meiosis. Mitosis maintains the chromosome number.
Calling the whole cell cycle mitosis.
Mitosis is only the nuclear division stage; growth and DNA replication come first.
Forgetting DNA replication.
It is what makes the daughter cells genetically identical, so it is usually worth a mark.
Exam tips
- State two identical daughter cells — both words matter.
- Mention DNA replication when explaining why cells are identical.
- Keep mitosis and meiosis clearly separate.
- Learn the three stages of the cell cycle in order.
Key terms
- Mitosis
- Nuclear division producing two genetically identical cells.
- Cell cycle
- The sequence of growth, DNA replication, mitosis and cell division.
- Daughter cell
- One of the cells produced by cell division.
- Replication
- The copying of DNA before cell division.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.