# The lac operon in E. coli is a well-studied example of gene regulation. Suggest how the lac repressor protein ensures that the lac genes are only transcribed when lactose is present in the cell.

> OCR A-Level Biology A (H420) — 6.1 Cellular control · Suggest · 4 marks

## Mark scheme (4 marks)

1. Understanding the role of the lac repressor protein in the regulation of the lac operon
2. Understanding how the lac repressor protein interacts with the lac genes and the RNA polymerase
3. Evaluating the importance of the lac repressor protein in regulating the lac operon
4. Providing a clear and concise explanation of the role of the lac repressor protein

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Source: [GradeNine](https://www.gradenine.co.uk/q/the-lac-operon-in-e-coli-5d2396fd) · Published by Druglandscape Ltd.