3 (a) 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
3 (a) Figure 4 shows cells from an onion root tip as seen using a light microscope.
Identify the stages of mitosis shown in cell Q and cell R.
| | cell Q ... show full transcript
Worked Solution & Example Answer:3 (a) 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
Cell Q is in telophase, as it shows the chromosomes beginning to de-condense and reform into nuclei. Cell R is in anaphase, as the chromosomes are being pulled apart towards opposite ends of the cell.
Step 2
Describe two processes that occur in cells during prophase.
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Answer
During prophase, the chromatin condenses into distinct chromosomes, making them visible under the microscope.
The nuclear envelope begins to break down, allowing the spindle fibers to interact with 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
Cytokinesis is the term used to describe the process that occurs after mitosis, leading to the division of the cytoplasm and the creation of two daughter cells.
Step 4
Which is this diameter in µm?
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Answer
0.075 mm is equal to 75 µm. This is calculated by converting millimeters to micrometers: 0.075 mm x 1000 = 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 adjust the microscope for x400 magnification, first ensure the slide is properly placed under the microscope stage. Begin with the lowest power objective lens and focus the image clearly. Then, switch to the x400 objective lens and use the fine focus knob to obtain a sharp image. Adjust the diaphragm as needed to enhance contrast.
Step 6
Describe the benefits and risks of using stem cell therapy to treat arthritis.
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Answer
Benefits:
Stem cells can differentiate into specific cell types, potentially helping to repair damaged joint cells.
They can replace damaged cells, potentially restoring function in affected areas.
Risks:
Newly formed cells may not function correctly, leading to complications.
Stem cells can continue to divide, potentially increasing the risk of tumor formation.
There may be side effects or rejection responses from the immune system.
