Multiple Choice
If the operator region (lacO) of the lac operon were mutated so that the repressor could no longer bind, what effect would this have on lactose metabolism in Escherichia coli?
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16. Regulation of Expression
The Lac Operon
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If E. coli bacteria are grown in the presence of lactose:
A
The repressor will bind the operator allowing transcription of the lac operon genes.
B
The repressor will not bind the operator preventing transcription of the lac operon genes.
C
The repressor will not bind the operator allowing transcription of the lac operon genes.
D
The repressor will bind the operator preventing transcription of the lac operon genes.
Verified step by step guidance1
Understand the role of the lac operon in E. coli: The lac operon is a set of genes responsible for the metabolism of lactose in E. coli. It includes genes that code for proteins needed to transport and break down lactose into glucose and galactose.
Identify the components involved: The lac operon consists of the promoter, operator, and structural genes. The repressor protein, produced by the lacI gene, can bind to the operator to block transcription.
Determine the effect of lactose presence: When lactose is present, it acts as an inducer by binding to the repressor protein. This binding changes the shape of the repressor, preventing it from attaching to the operator.
Analyze the transcription process: With the repressor unable to bind to the operator, RNA polymerase can bind to the promoter and transcribe the lac operon genes, leading to the production of enzymes that metabolize lactose.
Conclude the correct scenario: In the presence of lactose, the repressor will not bind the operator, allowing transcription of the lac operon genes to occur.
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