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Regulatory Proteins: Regulation by Repression (Quiz 2)

Why do different kinds of control mechanisms exist? Cells contain a diverse set of different mechanisms for controlling gene activation. In general, they type of mechanism controlling the synthesis of a gene product depends on the product’s function. If a product is involved in an catabolic pathway then gene expression will be stimulated by initial substrates of the pathway and repressed by final products of the pathway. Initial substrate molecules can either inactivate repressor proteins or induce activator proteins. Final product molecules would activate repressor proteins. Using these types of control mechanisms the genes for the pathway molecules could be turned on when there is a lot of the substrate molecules and turned off when there is a lot of the of the final product.

View the animation below, then complete the quiz to test your knowledge of the concept.






1Transcription is turned off by
A)induction
B)repression
C)activation
D)all of the above



2In regulation by repression
A)a sugar, such as lactose, acts as an inducer and combines with the repressor to prevent transcription
B)an inducer activates the activator so that it binds to DNA and prevents transcription
C)an amino acid activates the repressor so that the repressor binds to the operator and prevents transcription
D)an amino acid binds to the operator, blocking the repressor, allowing transcription to proceed



3In regulation by induction
A)an inducer inactivates the repressor so transcription can proceed
B)an inducer inactivates the repressor so transcription is stopped
C)an inducer activates the repressor so transcription can proceed
D)an inducer activates the repressor so transcription is stopped



4Negative control occurs when a repressor is inactivated by an inducer.
A)True
B)False



5An activator must react with its substrate before it can bind to DNA.
A)True
B)False







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