1.11 The stages of mitosis
6 exam questions worth 16 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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During which stage of mitosis do the chromosomes line up across the middle of the cell?
Choose one answer.
Correct Not quite: the answer is Metaphase
Mark scheme
B (Metaphase)
Model answer
B: Metaphase. In metaphase the chromosomes line up at the equator of the cell.
(a) Name the stage shown in A and the stage shown in D. (2 marks)
(b) Write the letters in the correct order, starting with B. (2 marks)
Mark scheme
(a)
- A: anaphase (1)
- D: metaphase (1)
(b)
- B, F, D, A, C, E (2)
- allow 1 mark if only one stage is in the wrong place
Model answer
(a) A is anaphase and D is metaphase.
(b) The correct order is B (interphase), F (prophase), D (metaphase), A (anaphase), C (telophase), E (cytokinesis).
Describe what happens to the chromosomes during anaphase.
Mark scheme
- spindle fibres shorten / pull (1)
- the chromatids (of each chromosome) are pulled apart to opposite ends / poles of the cell (1)
Model answer
The spindle fibres shorten and pull the two chromatids of each chromosome apart, to opposite ends of the cell.
Describe what happens in prophase.
Mark scheme
Any two from:
- the chromosomes coil up / become visible as two chromatids (1)
- the nuclear membrane breaks down (1)
- spindle fibres form (1)
Model answer
The chromosomes coil up and become visible, each as two joined chromatids. The nuclear membrane breaks down and spindle fibres form.
A scientist looks at a slice of a root tip. 80 of the 100 cells she counts are in interphase.
Explain why most of the cells are in interphase.
Mark scheme
- interphase is the longest stage (1)
- of the cell cycle (1)
- mitosis is a short stage / only a few cells are dividing at any one time (1)
Model answer
Interphase is the longest stage of the cell cycle, and mitosis is short, so at any one time only a few cells are dividing and most are in interphase.
Describe the events in telophase and cytokinesis.
Mark scheme
- the chromosomes reach opposite ends of the cell (1)
- the chromosomes uncoil / become thread-like again (1)
- a nuclear membrane forms around each group of chromosomes (1)
- the cytoplasm and cell membrane divide to make two identical cells (1)
Model answer
In telophase the chromosomes reach the ends of the cell and uncoil, and a nuclear membrane forms around each group. In cytokinesis the cytoplasm and cell membrane divide, making two identical daughter cells.
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