Figure 4 shows cells from an onion root tip as seen using a light microscope - Edexcel - GCSE Biology Combined Science - Question 3 - 2021 - Paper 1
Question 3
Figure 4 shows cells from an onion root tip as seen using a light microscope.
(i) Identify the stages of mitosis shown in cell Q and cell R.
| | cell Q | cel... show full transcript
Worked Solution & Example Answer:Figure 4 shows cells from an onion root tip as seen using a light microscope - Edexcel - GCSE Biology Combined Science - Question 3 - 2021 - Paper 1
Step 1
Identify the stages of mitosis shown in cell Q and cell R.
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Answer
The stages of mitosis are as follows:
Cell Q: A (metaphase)
Cell R: B (anaphase)
Step 2
Describe two processes that occur in cells during prophase.
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Answer
The chromatin condenses into visible chromosomes, making them easier to see under a microscope.
The nuclear membrane begins to break down, allowing the spindle fibers access to the chromosomes.
Step 3
State the term used to describe the process which occurs after mitosis, when the cell divides into two.
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Answer
The term used is 'cytokinesis'.
Step 4
The diameter of one cell in Figure 4 is 0.075 mm. Which is this diameter in µm?
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Answer
The correct answer is B (75 µm) since 0.075 mm is equal to 75 µm.
Step 5
Describe how to adjust the microscope to view the slide at a magnification of x400.
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Answer
To view the slide at a magnification of x400, follow these steps:
Start with the lowest power objective in place and secure the slide.
Use the coarse focus knob to bring the slide into focus.
Once focused, switch to the x400 magnification objective lens.
Use the fine focus knob to make minor adjustments for a clearer view.
Step 6
Discuss the benefits and risks of using stem cell therapy to treat arthritis.
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Answer
Benefits:
Stem cells can differentiate into specialized joint cells, potentially repairing damaged tissues.
They may reduce the symptoms of arthritis by replenishing damaged cells.
Risks:
New cells may not function properly, leading to complications.
There is a risk of side effects or rejection by the body’s immune system.
Stem cells have the potential to continue dividing, which could lead to cancer.
