Download Make an Operon

Modeling Gene Regulation in Bacteria
AP Biology
Objectives:
Make a model of the lac or trp operon
Demonstrate the mechanisms that regulate gene expression in operons
Simulate the transcription of the genes in the operon
Make a model of an operon
1. Your teacher will assign your group either the lac or trp operon to build.
2. Using the materials available in the classroom design and build an operon model. Your
model must include the following parts: promoter, regulatory gene, operator, RNA
polymerase, repressor, co-repressor or inducer, mRNA, structural genes of the operon.
3. If you are building the lac operon, build your operon in the “turned off” mode. If you are
building the trp operon, build it in the “turned on” mode.
4. Draw your model in your lab book and label the parts.
5. Now activate your lac operon by adding the inducer and removing the repressor or
inactivate your trp operon by adding the co-repressor and activating the repressor.
6. Call your teacher over to demonstrate your model. Once your teacher approves, draw this
new model in your lab book and label the parts.
Background questions:
1. Define: gene.
2. What is the role of RNA polymerase in protein synthesis?
3. What is the role of ribosomes in protein synthesis??
4. What are the roles of an operator, promoter and structural genes within an operon
5. How does the presence or absence of lactose affect the lac operon? How does the presence
or absence of tryptophan affect the trp operon?
6. What is a regulator gene?
Analysis and Conclusion Questions
1. Describe in words what takes place when your operon is activated and inactivated.
2. What substance serves as the repressor in the trp operon? As the activator in the lac operon?
3. How might a mutation in the regulator gene affect the operon?
4. How would the loss of the promoter site affect the production of enzymes by the operon?
5. How is the function of an operon similar to feedback inhibition?