Fundamentals of Biology

Gene Regulation and the Lac Operon

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Session Overview

Cells with the same DNA can look and function differently from each other; consider a photoreceptor cell and muscle cell. The difference between these two cells is the result of differential gene expression. Some genes are transcribed and translated in all cells at about the same level, but other genes may be expressed in one cell type but not another. This session will briefly outline some general principles of gene regulation. In addition, a specific example of gene regulation in bacteria will be presented in detail. Learning Objectives To recall and understand the different mechanisms working together to regulate the Lac operon. To distinguish positive and negative regulatory mechanisms. To predict the phenotype caused by different mutations within the Lac operon. To justify the benefit to an organism of regulating genes.

Session Activities

Lecture Video

For this session, watch the first 30 minutes of the video lecture called “Gene Regulation” by Prof. Eric Lander recorded in 2004.

• Gene Regulation

Check Yourself

Question 1

What is the function of the protein encoded by the LacZ gene?

Turns glucose into ATP. close

Turns glucose into lactose. close

Turns glucose into pyruvate. close

Turns lactose into glucose and galactose. check

Check

Question 2

When should E. coli produce beta-galactosidase?

High glucose, high lactose. close

High glucose, low lactose. close

Low glucose, high lactose. check

Low glucose, low lactose. close

Check

Session Activities

Help Session Video

Watch the short video of Sera Thornton explaining the lac operon.

• The lac operon

Practice Problems

• Problems (PDF)
• Solutions (PDF)

Further Study

Suggested topics for further study in an introductory-level Biology textbook

• The Lac operon
• Gene regulation

Useful Links

• lac operon

Study Guides

• Diagram of lac operon (PDF)

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