Explain what happens during the cell cycle, including the stages of mitosis, to produce two genetically identical daughter cells.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
The cell cycle is a series of events that takes place in a cell, involving cell growth, DNA replication and cell division. The cycle includes a long stage called interphase followed by mitosis and cytokinesis.
Model answer (5 marks)
During interphase the cell grows and the DNA is replicated, so each chromosome is copied into two identical sister chromatids.
In mitosis the duplicated chromosomes are separated:
1. In prophase the chromosomes condense and the nuclear envelope breaks down.
2. In metaphase the chromosomes line up at the metaphase plate (cell equator).
3. In anaphase the sister chromatids are pulled apart by spindle fibres to opposite poles of the cell.
4. In telophase new nuclear envelopes form around the two sets of chromosomes.
Cytokinesis then divides the cytoplasm, producing two new daughter cells.
The two daughter cells are genetically identical to each other and to the parent cell, and each is diploid, containing a full set of chromosomes.
In mitosis the duplicated chromosomes are separated:
1. In prophase the chromosomes condense and the nuclear envelope breaks down.
2. In metaphase the chromosomes line up at the metaphase plate (cell equator).
3. In anaphase the sister chromatids are pulled apart by spindle fibres to opposite poles of the cell.
4. In telophase new nuclear envelopes form around the two sets of chromosomes.
Cytokinesis then divides the cytoplasm, producing two new daughter cells.
The two daughter cells are genetically identical to each other and to the parent cell, and each is diploid, containing a full set of chromosomes.
Examiner tips
- Use the word ‘interphase’ to show the growth and DNA replication stage. Mention the four mitotic stages in order, especially metaphase and anaphase. State that cytokinesis follows mitosis. Conclude that the daughter cells are genetically identical and diploid.
- common_mistakes
- :
- Forgetting to mention DNA replication in interphase. Mixing up the order of mitotic stages. Failing to state that the daughter cells are genetically identical and diploid.
Mark scheme (5 marks)
- During interphase, the cell grows and DNA replication occurs (so each chromosome is copied)
- During metaphase, chromosomes align at the cell equator
- During anaphase, chromatids are pulled to opposite poles of the cell by spindle fibres
- Cytokinesis divides the cytoplasm to produce two new daughter cells
- The two daughter cells are genetically identical to each other and to the parent cell / both are diploid cells containing a full set of chromosomes
Key terms in this question
Related
- All Edexcel A-Level Biology A: Salters-Nuffield (9BN0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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