Multiple Choice
In the lac operon, the product of the structural gene lacZ is capable of ________.
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12. Gene Regulation in Prokaryotes
Lac Operon
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What happens to the lac operon when lactose concentration is high?
A
The lac operon is activated, and lactose is synthesized
B
The lac operon is activated, and lactose is broken down
C
The lac operon is repressed, and lactose is synthesized
D
The lac operon is repressed, and lactose is broken down
Verified step by step guidance1
Understand the role of the lac operon: The lac operon is a set of genes responsible for the metabolism of lactose in bacteria, primarily E. coli. It includes genes that code for proteins needed to transport and break down lactose into glucose and galactose.
Identify the components of the lac operon: The operon consists of three structural genes (lacZ, lacY, and lacA), a promoter, an operator, and a repressor protein. The lacZ gene encodes β-galactosidase, which breaks down lactose.
Recognize the effect of lactose on the lac operon: When lactose is present, it acts as an inducer by binding to the repressor protein, causing a conformational change that prevents the repressor from binding to the operator. This allows RNA polymerase to transcribe the operon's genes.
Determine the outcome of high lactose concentration: With the repressor inactivated by lactose, the operon is 'turned on' or activated, leading to the transcription of the genes necessary for lactose metabolism.
Conclude the process: The activation of the lac operon results in the production of enzymes that break down lactose into simpler sugars, thus the correct statement is that the lac operon is activated, and lactose is broken down.
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