Identify stages of mitosis in cell images
Use chromosome condensation, alignment, separation and re-formation of nuclei to identify mitosis stages in diagrams and photomicrographs.
AS Level · Cambridge International Biology 9700, 2028–2030. These lessons explain cell-cycle concepts and image interpretation. Written practice is self-checked; it does not demonstrate practical microscopy competence or replace teacher-reviewed assessment.
Before you begin
- Recognise DNA as genetic material and use the terms cell, nucleus and chromosome accurately.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What is the most diagnostic feature of metaphase?
What you will learn
- Identify prophase, metaphase, anaphase and telophase in diagrams and photomicrographs
- Support a stage identification with visible evidence
Look for the most diagnostic feature
Prophase: condensed chromosomes are visible but not aligned; the nuclear envelope is breaking down and the spindle is forming. Metaphase: chromosomes align at the equator.
Anaphase: sister chromatids have separated and move towards opposite poles. Telophase: chromosome sets are at the poles and new nuclear envelopes are forming. A plant cell may also show a cell plate; an animal cell may show a cleavage furrow.
Use visible evidence, not cell shape alone
Identify the chromosome arrangement first, then use the spindle, nuclei and cell boundary as supporting evidence. A cell’s overall shape or size alone is not enough to identify a stage.
A thin section or photomicrograph may not show every structure clearly. State the feature visible in the image and avoid claiming an unseen structure. If two stages look similar, compare whether chromosomes are aligned, separating or already at opposite poles.
Pause and explain
A cell image shows chromatids moving to opposite poles. Which stage is visible?
Worked example
An image shows condensed chromosomes that are not aligned, and the nuclear boundary is disappearing. Identify the stage and give two observations.
Show the worked solution
- Condensed, unaligned chromosomes indicate prophase.
- A disappearing nuclear boundary supports prophase.
Answer The cell is in prophase. The chromosomes are condensed but not aligned at the equator, and the nuclear envelope is breaking down.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Identify the stage in an image with condensed chromosomes spread through the nucleus but not aligned, and give one reason.
Give me a hint
Compare the image with the equatorial alignment expected in metaphase.
Compare my reasoning
- Chromosomes are condensed.
- They are not aligned at the equator, supporting prophase.
The image shows prophase because chromosomes are condensed but not aligned at the equator.
Look for these in your work
- Stage correct
- Visible evidence cited
A photomicrograph shows chromosomes at both poles and two nuclei beginning to form. Name the stage and state the evidence.
Give me a hint
Look for the stage after chromatids have separated.
Compare my reasoning
- Chromosome sets have reached opposite poles.
- New nuclear envelopes are forming in telophase.
The cell is in telophase: chromosome sets are at opposite poles and new nuclear envelopes are forming around them.
Look for these in your work
- Stage identified
- Two visible features used
Two images show condensed chromosomes. In image A, they form a line at the equator; in image B, chromatids move apart. Identify each stage.
Give me a hint
Use position and movement, not condensation alone.
Compare my reasoning
- Equatorial alignment indicates metaphase.
- Movement to opposite poles indicates anaphase.
Image A shows metaphase because chromosomes align at the equator. Image B shows anaphase because sister chromatids are moving towards opposite poles.
Look for these in your work
- Both stages correct
- Different diagnostic features stated
Common mistakes
- Identifying metaphase simply because chromosomes look condensed
- Calling separated chromatids in anaphase “two daughter cells”
- Inferring an invisible spindle or envelope without image evidence
What can you explain now?
What is the most diagnostic feature of metaphase?
Compare with the explanation
Chromosomes aligned at the equator
Equatorial alignment identifies metaphase.
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Make it stick
Which visible chromosome features distinguish prophase, metaphase, anaphase and telophase?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.