CAIE A Level Biology 9700 · Inheritance

Inheritance: explain question

Explain5 marksStandard

The lac operon in Escherichia coli is a classic model of gene regulation in prokaryotes.

(a) With reference to this operon, explain the difference between a structural gene and a regulatory gene.

(b) Using the lac operon as an example, explain the difference between inducible and repressible enzymes.

How this question is marked

5 marks, so the mark scheme is looking for about 5 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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