CAIE A Level Biology 9700 · Nucleic acids and protein synthesis
The coding strand of a short bacterial gene is 5'-ATG GCT CAG TGA-3'.
(a) Explain how this DNA sequence is used to produce a polypeptide.
(b) A mutation deletes the fourth base (counting from the 5' end) of this coding strand. Explain how this mutation would alter the polypeptide produced.
6 marks, so the mark scheme is looking for about 6 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
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