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A student prepared a stained squash of cells from the root tips of garlic to calculate a mitotic index - AQA - A-Level Biology - Question 3 - 2022 - Paper 3
Question 3
A student prepared a stained squash of cells from the root tips of garlic to calculate a mitotic index. He: 1. cut the end 5 mm from 10 garlic roots 2. placed the ro... show full transcript
Worked Solution & Example Answer:A student prepared a stained squash of cells from the root tips of garlic to calculate a mitotic index - AQA - A-Level Biology - Question 3 - 2022 - Paper 3
Step 1
Suggest why the student soaked the root tips in hydrochloric acid in step 2.
Answer
The student soaked the root tips in hydrochloric acid to:
- Break down links between cell walls, allowing the cells to separate more easily.
- Hydrolyze the cellulose in the cell walls, enabling better access to the cells for staining.
Step 2
Explain why pressing the coverslip downwards enabled the student to observe the stages of mitosis.
Answer
Pressing the coverslip downwards creates a thin layer of cells, which makes it easier to visualize the individual cells under the microscope. It also spreads out the cells, enhancing the clarity of each stage of mitosis, allowing for better observation.
Step 3
Name the stage of mitosis shown in cell G. Explain the appearance of this cell.
Answer
Stage of mitosis: Anaphase.
Explanation: In anaphase, the chromatids are pulled apart towards opposite poles of the cell. The cell will appear elongated with the chromosomes separated, moving toward the ends.
Step 4
Step 5
Apart from student errors, suggest two explanations why.
Answer
- The garlic roots might have been of different ages, leading to variations in the rates of mitosis.
- The environmental conditions where the garlic was grown may have varied, such as differences in temperature and nutrient availability, affecting growth and cell division rates.