AQA · A-Level · Biology
Course version: 7402 · Version from Sept 2016
The behaviour of chromosomes during interphase, prophase, metaphase,…
Full specification wording
All cells arise from other cells: The behaviour of chromosomes during interphase, prophase, metaphase, anaphase and telophase of mitosis.
In interphase the chromosomes are uncondensed chromatin and cannot be seen as separate structures; the DNA is replicated so each becomes two sister chromatids.
Checked against the AQA 7402 specification (opens in a new tab) on .
- Point 5 of 14
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
In interphase the chromosomes are uncondensed chromatin and cannot be seen as separate structures; the DNA is replicated so each becomes two sister chromatids. In prophase the chromosomes condense by supercoiling and become visible as two chromatids joined at a centromere, the nuclear envelope breaks down, the nucleolus disappears, and the spindle forms with its poles at opposite ends of the cell. In metaphase the chromosomes line up along the equator, attached by their centromeres to spindle fibres running to both poles. In anaphase the centromeres divide and the spindle fibres shorten, pulling the sister chromatids apart to opposite poles centromere first, which is what gives them their V shape; this requires ATP from mitochondria. In telophase the chromatids reach the poles, uncoil back into chromatin, a nuclear envelope reforms around each group and the nucleolus reappears.
What earns the marks
- Prophase: chromosomes condense and become visible, the nuclear envelope breaks down and the spindle forms.
- Metaphase: chromosomes line up along the equator, attached by their centromeres to spindle fibres.
- Anaphase: the centromeres divide and the chromatids are pulled to opposite poles of the cell.
- Telophase: chromatids reach the poles, uncoil, and a nuclear envelope reforms around each group.
- Correctly naming a stage from an image and explaining the appearance by the event causing it.
Common mistakes and how to put them right
Naming a stage anaphase I when the question is about mitosis.
Put it right: The mark scheme rejects the meiotic label outright.
Saying homologous chromosomes are separated in anaphase, when it is sister chromatids, with homologous chromosomes explicitly rejected.
Describing chromosomes lining up in pairs at the equator in metaphase, which is metaphase I of meiosis.
Saying individual chromosomes are visible during interphase.
Leaving out the breakdown and reformation of the nuclear envelope, which carries marks in prophase and telophase.
Exam tips
- Learn one distinguishing visible feature per stage so you can identify a micrograph in seconds: scattered threads, a single line, two moving groups, two dense groups.
- Chromatids is the safer word from anaphase onwards; chromosomes is accepted but homologous chromosomes is rejected.
- In a describe the behaviour question, track the chromosomes themselves and do not drift into describing the spindle only.
Try the lesson
The start of the All cells arise from other cells: The behaviour of chromosomes during interphase, prophase, metaphase, anaphase and telophase of mitosis. lesson, made from checked teaching notes for this specification point.
Have a go first
During which stage of mitosis do the chromatids of each chromosome separate and move to opposite poles of the cell?
Listen
In interphase the chromosomes are uncondensed chromatin and cannot be seen as separate structures; the DNA is replicated so each becomes two sister chromatids. In prophase the chromosomes condense by supercoiling and become visible as two chromatids joined at a centromere, the nuclear envelope breaks down, the nucleolus disappears, and the spindle forms with its poles at opposite ends of the cell. In metaphase the chromosomes line up along the equator, attached by their centromeres to spindle fibres running to both poles. In anaphase the centromeres divide and the spindle fibres shorten, pulling the sister chromatids apart to opposite poles centromere first, which is what gives them their V shape; this requires ATP from mitochondria. In telophase the chromatids reach the poles, uncoil back into chromatin, a nuclear envelope reforms around each group and the nucleolus reappears. A strong answer earns marks for these points. prophase: chromosomes condense and become visible, the nuclear envelope breaks down and the spindle forms. metaphase: chromosomes line up along the equator, attached by their centromeres to spindle fibres. anaphase: the centromeres divide and the chromatids are pulled to opposite poles of the cell. telophase: chromatids reach the poles, uncoil, and a nuclear envelope reforms around each group. Exam tip: Learn one distinguishing visible feature per stage so you can identify a micrograph in seconds: scattered threads, a single line, two moving groups, two dense groups.
Key words
Say what each word means before you turn the card.
chromosome condensation
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equator alignment
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chromatid separation
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nuclear envelope breakdown and reformation
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See every definition
- chromosome condensation
- Chromosomes condense by supercoiling and become visible as two chromatids joined at a centromere.
- equator alignment
- Chromosomes line up along the equator, attached by their centromeres to spindle fibres running to both poles.
- chromatid separation
- The centromeres divide and the spindle fibres shorten, pulling the sister chromatids apart to opposite poles centromere first.
- nuclear envelope breakdown and reformation
- The nuclear envelope breaks down in prophase and reforms around each group of chromatids in telophase.
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