Multiple Choice
If the trp regulatory gene mutates so that the repressor protein can no longer bind to tryptophan what will be the result?
16. Regulation of Expression
The Trp Operon
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Under what conditions does the trp repressor block transcription of the trp operon?
A
When the repressor binds to the inducer.
B
When the repressor binds to tryptophan.
C
When the repressor is not bound to tryptophan.
D
When the repressor is not bound to the operator.
Verified step by step guidance1
Understand the role of the trp operon: The trp operon is a group of genes that are used to produce tryptophan, an essential amino acid. It is regulated by the trp repressor, which can block transcription when bound to the operator region of the operon.
Identify the function of the trp repressor: The trp repressor is a protein that can bind to the operator region of the trp operon to prevent transcription. Its activity is influenced by the presence of tryptophan.
Determine the conditions for repressor binding: The trp repressor can only bind to the operator when it is bound to tryptophan. Tryptophan acts as a corepressor, changing the shape of the repressor so it can attach to the operator.
Analyze the effect of tryptophan binding: When tryptophan levels are high, it binds to the trp repressor, enabling the repressor to bind to the operator and block transcription of the trp operon. This prevents the synthesis of tryptophan when it is already abundant.
Conclude the conditions for blocking transcription: Transcription of the trp operon is blocked when the trp repressor is bound to tryptophan, allowing it to attach to the operator and inhibit gene expression.
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