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Describe the role of DNA polymerase in the semi-conservative replication of DNA - AQA - A-Level Biology - Question 5 - 2020 - Paper 1
Question 5
Describe the role of DNA polymerase in the semi-conservative replication of DNA. It took less time for 25% of cells with cyclin D to be undergoing DNA replication t... show full transcript
Worked Solution & Example Answer:Describe the role of DNA polymerase in the semi-conservative replication of DNA - AQA - A-Level Biology - Question 5 - 2020 - Paper 1
Step 1
Describe the role of DNA polymerase in the semi-conservative replication of DNA.
Answer
DNA polymerase is essential in semi-conservative replication as it catalyzes the addition of nucleotides to the growing DNA strand. Specifically, it joins adjacent DNA nucleotides by forming phosphodiester bonds through condensation reactions, ensuring the new strand is complementary to the template strand.
Step 2
Use Figure 5 to calculate this time difference as a percentage decrease. Show your working.
Answer
To find the percentage decrease in time taken for cells with cyclin D compared to those without:
- Let the time for cells without cyclin D be T1.
- Let the time for cells with cyclin D be T2.
- The formula for percentage decrease is: ext{Percentage Decrease} = rac{T1 - T2}{T1} imes 100
- Substitute the values obtained from Figure 5 into the formula.
Step 3
Describe how an enzyme can be phosphorylated.
Answer
An enzyme can be phosphorylated through the addition of a phosphate group, typically from ATP. This process involves the transfer of the phosphate group from ATP to the enzyme, leading to a conformational change that can activate or inhibit the enzyme's function.
Step 4
Use Figure 5 to suggest why higher than normal concentrations of cyclin D could result in a tumour.
Answer
Higher concentrations of cyclin D could lead to an accelerated cell cycle, resulting in shorter interphase and earlier initiation of DNA replication. This rapid division may contribute to uncontrolled cell growth, increasing the likelihood of mutations and potentially resulting in tumor formation.