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Question 1
A scientist investigated the growth rate of the bacterium Bacillus sonorensis. |
a) | Describe how these bacterial cells replicate by binary fission.
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b) | The scientist measured the mass of bacterial cells in picograms. 1 pg (picogram) = 1 x 10-12 g Calculate how many grams are in 720 pg.
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c) | Suggest two ways in which the environmental conditions could be altered to increased the growth rate of the bacteria.
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Question 2
The diagram below shows an example of a chromosome. |
a) | Name the part labelled X in the diagram above.
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b) | Describe the role of part X in the process of mitosis.
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c) | Mitosis is a cell process used by organisms throughout their lifetime. Explain why mitosis is an important cell process.
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d) | Interphase is one of the stages of mitosis. Describe what occurs during interphase to prepare a cell for division.
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Question 3
Vincristine is a chemotherapy drug that works by stopping cancer cells from separating into two new cells. It prevents mitosis by interfering with the formation of spindle fibres. However, this drug has also been found to affect healthy cells. |
a) | Name the stages of mitosis in the correct order.
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b) | Explain why interfering with the formation of spindle fibres stops the cell cycle.
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c) | Suggest why vincristine is successfully used as a treatment for some cancers even though it also affects healthy cells.
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d) | Explain how the behaviour of chromosomes in mitosis results in two genetically identical cells.
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Question 4
A student viewed some meristem cells in a microscope. One of the cells seen is shown in the diagram below. |
a) | Name the stage of mitosis taking place in the cell shown above.
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b) | Describe what happens in this stage of mitosis to produce two genetically identical cells.
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c) | When preparing her microscope slide, the student made sure to use the root tip of the plant. Explain why.
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d) | The student counted the number of cells in each stage of mitosis. She counted 150 cells in total, but only 8 cells were in the process of metaphase. One cell cycle of this plant tissue takes 12 hours. Calculate how many minutes these cells spend in metaphase.
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Question 5
The statements below describe some of the stages in the cell cycle. A - The cytoplasm divides. B - The nuclear envelope disappears. C - The chromosomes line up on the equator of the spindle. D - The chromatids are pulled to opposite poles. E - The chromosomes condense. |
a) | List the statements A to E in the correct order as they take place in the cell cycle.
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b) | Name the stage of mitosis described in statement D.
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c) | The diagram below shows how the mass of DNA per cell changed during the process of mitosis. Describe and explain the change in mass of DNA at the stage labelled B in the diagram above.
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d) | Describe and explain the change in the mass of DNA at the stage labelled D in the diagram above.
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Question 6
A scientist investigated the effect of a chemical called colchicine on the process of cell division. Colchicine interrupts the cell cycle by inhibiting mitosis. The scientist added colchicine to one set of cells and used a set of genetically identical cells with no colchicine as a control. He left each set of cells for 8 hours and then calculated the mean percentages of cells in each stage of mitosis. His results are shown below. |
a) | Explain why the scientist examined 200 cells in each set to calculate the mean percentage.
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b) | The scientist did not record the percentage of cells undergoing interphase. Explain how the scientist could have identified which cells were in interphase when looking in the microscope.
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c) | When preparing to observe the cells, the scientist placed the tissue sample in a slightly hypotonic solution. This caused chromosomes to move apart to make them easier to identify when observed in the microscope. Suggest how a hypotonic solution moved the chromosomes apart.
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d) | Use the results table to explain how colchicine affects the process of mitosis.
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Question 7
A scientist investigated how the mean distance between chromosomes and the poles of the spindle changed during the process of mitosis. His results are shown in the graph below. |
a) | Calculate the rate of movement of the chromosomes between 2,000 s and 2,500 s. Give your answer in nanometres per minute.
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b) | Name the stage of mitosis taking place between 1,200 s and 1,800 s.
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c) | Describe the role of the spindle fibres during the stage of mitosis between 1,200 s and 1,800 s.
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d) | Name the stage of mitosis taking place after 1,800 s and explain how chromosomes behave during this stage.
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Question 8
The diagram below shows the nucleus of a cell undergoing the process of mitosis. |
a) | Identify structures X and Y labelled in the diagram above.
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b) | Name the stage of mitosis in which the chromosomes condense and the spindle starts to form.
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c) | Describe the function of the centromere during the process of mitosis.
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Question 9
A student investigated the process of cell division in a garlic root. The diagram below shows some of the cells she observed in the microscope. |
a) | Which stage of mitosis is shown in cell A in the diagram above?
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b) | Describe the evidence that cell B in the diagram above is in anaphase.
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c) | When preparing her microscope slide, the student added a stain solution to the cells and covered with a coverslip. Explain why before viewing the slide, she pressed down firmly on the cover slip.
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d) | Mitosis is only one part of the cell cycle. Describe what happens in the other stages of the cell cycle.
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