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Figure 1 shows all the chromosomes present in one human cell during mitosis - AQA - A-Level Biology - Question 1 - 2018 - Paper 1
Question 1
Figure 1 shows all the chromosomes present in one human cell during mitosis. A scientist stained and photographed the chromosomes. In Figure 2, the scientist has... show full transcript
Worked Solution & Example Answer:Figure 1 shows all the chromosomes present in one human cell during mitosis - AQA - A-Level Biology - Question 1 - 2018 - Paper 1
Step 1
Give two pieces of evidence from Figure 1 that this cell was undergoing mitosis. Explain your answers.
Answer
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The individual chromosomes are visible because they have condensed. This suggests that the cell is preparing for division as chromosomes condense to become more distinct during mitosis.
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Each chromosome is made up of two chromatids because DNA has replicated. This is indicative of the mitotic phase where replication has occurred prior to cell division.
Step 2
Step 3
Step 4
Suggest one way the structure of the chromosome could differ along its length to result in the stain binding more in some areas.
Answer
The differences in base sequences of DNA or variations in histone interaction could lead to differing degrees of condensation, causing some areas to attract the stain more than others.
Step 5
Step 6
Give two ways in which the arrangement of prokaryotic DNA is different from the arrangement of the human DNA in Figure 1.
Answer
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Prokaryotic DNA is circular as opposed to linear in eukaryotes.
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Prokaryotic DNA is not associated with proteins/histones, whereas human DNA is tightly regulated with histone proteins.