Photo AI
1. Describe the role of DNA polymerase in the semi-conservative replication of DNA - AQA - A-Level Biology - Question 5 - 2020 - Paper 1
Question 5
1. Describe the role of DNA polymerase in the semi-conservative replication of DNA. 2. It took less time for 25% of cells with cyclin D to be undergoing DNA replica... show full transcript
Worked Solution & Example Answer:1. 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 plays a crucial role in the semi-conservative replication of DNA by joining adjacent DNA nucleotides together. It catalyzes the condensation reaction that forms phosphodiester bonds between nucleotides, ensuring that the newly synthesized strand is complementary to the template strand.
Step 2
It took less time for 25% of cells with cyclin D to be undergoing DNA replication than for 25% of cells without cyclin D.
Answer
To calculate the percentage decrease in time:
- Let the time taken for 25% of cells without cyclin D be represented as T1.
- Let the time taken for 25% of cells with cyclin D be represented as T2.
- Use the formula for percentage decrease:
- Assuming you have the specific times from Figure 5, plug in the values accordingly to calculate the percentage difference.
Step 3
Describe how an enzyme can be phosphorylated.
Answer
An enzyme can be phosphorylated by the addition of a phosphate group (PO₄²⁻) to its amino acid residues, typically via a reaction catalyzed by a kinase. This process often involves the transfer of a phosphate group from ATP (adenosine triphosphate) to the enzyme, which can alter the enzyme's activity, stability, or interactions with other molecules.
Step 4
Use Figure 5 to suggest why higher than normal concentrations of cyclin D could result in a tumour.
Answer
Higher than normal concentrations of cyclin D can lead to an accelerated progression through the cell cycle, particularly shortening the interphase. This can cause cells to replicate DNA at a faster rate, increasing the likelihood of mutations. As a result, uncontrolled cell division may occur, leading to the development of a mass or group of abnormal or excessive cells, commonly associated with tumours.