CAIE A Level Biology 9700 · Nucleic acids and protein synthesis
A gene in a bacterium has the following coding (non-template) strand sequence: 5'-ATG GCT CAA TAC GGT-3'
In one mutant, a substitution mutation changes the sixth base (counting from the 5' end) from T to A. In another mutant, a deletion mutation removes the seventh base.
Explain how each of these mutations would affect the polypeptide produced from this gene.
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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