Photo AI
Use the Data Booklet to help you answer this question about DNA - AQA - A-Level Chemistry - Question 9 - 2018 - Paper 2
Question 9
Use the Data Booklet to help you answer this question about DNA. Figure 2 shows a fragment of a DNA double helix. The letters A, C, G and T represent the four base... show full transcript
Worked Solution & Example Answer:Use the Data Booklet to help you answer this question about DNA - AQA - A-Level Chemistry - Question 9 - 2018 - Paper 2
Step 1
Step 2
Deduce the total number of hydrogen bonds formed between the five bases in each strand.
Answer
The total number of hydrogen bonds formed between the five bases is 12. This is because:
- A pairs with T, forming 2 hydrogen bonds.
- C pairs with G, forming 3 hydrogen bonds. In this case, there are two pairs of A-T and C-G interactions, leading to the total:
Number of A-T pairs: 2 (2 hydrogen bonds each) Number of C-G pairs: 3 (3 hydrogen bonds each)
Calculating the numbers yields:
Total bonds = 2(2) + 2(3) = 4 + 6 = 12.
Step 3
Base A is part of a nucleotide in the DNA strand shown in Figure 2.
Answer
To complete the structure of the nucleotide that contains base A:
- Draw the 2-deoxyribose sugar ring structure.
- Attach a phosphate group to the 5' carbon of the deoxyribose.
- Attach base A to the 1' carbon of the deoxyribose.
The complete nucleotide structure, showing base A, will have the phosphate on the left and base A on the right of the sugar.