A-LevelBiologyThe mitotic cell cycle9700/21 · Oct/Nov 2024 · Q64 Marks
Fig. 6.1 shows a plant cell in a stage of mitosis. [Figure 6.1]
- (a)Some of the structures shown in Fig. 6.1 contain DNA. Use a line labelled D on Fig. 6.1 to indicate one of these structures.[1]
- (b)Name the stage of mitosis shown in Fig. 6.1.[1]
- (c)Colchicine is a chemical used by scientists to study mitosis. This chemical inhibits the organisation of the microtubules in prophase of mitosis. The cell shown in Fig. 6.1 had not been treated with colchicine. Explain the evidence in Fig. 6.1 that shows the cell had not been treated with colchicine.[2]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2024). The mark or mark type is shown in brackets.
- 6(a) line pointing to any chromatid ;
- 6(b) anaphase;
- 6(c) any two from: (fully formed) spindle seen / spindle fibres, are visible;
- idea that chromatids are attached to, the spindle fibres / (spindle) microtubules ;
- idea that chromosomes would have orientated at the equator (ready for anaphase);
- sister chromatids have separated (Fig. 6.1) because, spindle fibres have contracted / microtubules have disassembled / AW;
- in anaphase so has, completed /AW, prophase / metaphase ;
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