(a) Fig. 4.1 shows part of a DNA molecule.
[Figure 4.1]
Use Fig. 4.1 to explain how the structure of mRNA differs from the structure of DNA.
(b) Fig. 4.2 shows:
• the first seven amino acids of the β chain of haemoglobin
• the first amino acid in the sequence is valine (Val)
• the 21 base pairs in the sequence of DNA that code for these seven amino acids.
[Figure 4.2]
Table 4.1 shows the triplets of bases that code for seven amino acids.
Using Fig. 4.2 and Table 4.1, state what will happen to the sequence of amino acids in the first part of the β chain of haemoglobin:

Q: What topic does this question test?

This question tests Nucleic acids and protein synthesis in A-Level Biology (syllabus code 9700). It is worth 16 marks.

Q: Which exam paper is this question from?

This question appeared in the Cambridge A-Level Biology May/June 2017 examination, Paper 2 Variant 1 (9700_s17_qp_21.pdf).

Question

(a) Fig. 4.1 shows part of a DNA molecule.
[Figure 4.1]
Use Fig. 4.1 to explain how the structure of mRNA differs from the structure of DNA.
(b) Fig. 4.2 shows:
• the first seven amino acids of the β chain of haemoglobin
• the first amino acid in the sequence is valine (Val)
• the 21 base pairs in the sequence of DNA that code for these seven amino acids.
[Figure 4.2]
Table 4.1 shows the triplets of bases that code for seven amino acids.
Using Fig. 4.2 and Table 4.1, state what will happen to the sequence of amino acids in the first part of the β chain of haemoglobin:

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