Identify stages of meiosis in images
Use chromosome arrangement, spindle position and centromere behaviour to interpret meiosis diagrams and photomicrographs.
A Level; Cambridge International Biology 9700, 2028–2030. Written answers are self-checked; this is not practical-skills certification.
Before you begin
- Genes are DNA sequences that can be inherited; meiosis and fertilisation link parental genomes.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which feature distinguishes metaphase I from metaphase II?
What you will learn
- Identify the named stages of meiosis from diagrams and photomicrographs
- Use chromosome arrangement and separation to distinguish meiosis I from meiosis II
Original teaching model. Counts, source combinations and sample records are stipulated; drawings are schematic.
| Feature | Meaning |
|---|---|
| Diploid precursor | 8 chromosomes in two complete four-type sets |
| Normal meiotic products | 4 per nucleus; one of each required type |
| Different supplied combinations | Both complete; allele records can differ |
| Later fusion and limits | 4 + 4 = 8; wider teaching and assessments remain pending |
Build the genetic explanation
Stage identification depends on visible evidence. Paired homologues at the equator indicate metaphase I; single chromosomes at the equator indicate metaphase II. Homologues moving apart while chromatids remain joined indicate anaphase I. Sister chromatids moving apart indicate anaphase II. Nuclear envelopes and cell boundaries help distinguish telophase and cytokinesis.
Check the evidence and limits
A single still image may not show spindle fibres or the whole cell. Use multiple clues and avoid identifying a stage from chromosome count alone when replication state and sectioning are unclear.
Pause and explain
A micrograph is cropped so that no cell boundary or spindle poles are visible. What should you do before naming the stage?
Worked example
A photomicrograph shows homologous pairs at the equator. Which stage is most likely?
Show the worked solution
- The chromosomes are arranged as pairs.
- Paired homologues characterize metaphase I.
Answer Metaphase I.
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Test this topic →From guided practice to a new situation
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.
A diagram shows centromeres still joined while homologous chromosomes move toward opposite poles. Identify the stage.
Give me a hint
Set out the alleles or steps before deciding the outcome.
Compare my reasoning
- Homologues are separating.
- Sister chromatids remain joined.
Anaphase I: homologous chromosomes separate while sister chromatids remain joined.
Look for these in your work
- Genetic terms used correctly
- Steps linked
A cell shows single chromosomes aligned at its equator after the first meiotic division. Identify the stage.
Give me a hint
Use the given evidence and state your assumptions.
Compare my reasoning
- The second division is occurring.
- Chromosomes align singly in metaphase II.
Metaphase II: individual chromosomes align singly at the equator in the second meiotic division.
Look for these in your work
- Prediction or interpretation supported
- Limits stated
A micrograph is cropped so that no cell boundary or spindle poles are visible. What should you do before naming the stage?
Give me a hint
Apply the inheritance or gene-control model to the new context.
Compare my reasoning
- Inspect chromosome pairing and centromere state.
- Check whether the image provides enough evidence.
Use visible chromosome arrangement and whether chromatids or homologues are separating. If those features are not clear, state that the image is insufficient for a confident stage identification.
Look for these in your work
- Model applied accurately
- Unsupported certainty avoided
Common mistakes
- Confusing metaphase I pairs with metaphase II single chromosomes
- Inferring all events from one incomplete cross-section
What can you explain now?
Which feature distinguishes metaphase I from metaphase II?
Compare with the explanation
Pairs of homologues align in metaphase I
In metaphase II individual chromosomes align singly.
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Make it stick
Which image features help distinguish metaphase I from metaphase II?
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.