Concept explainers
Compare and contrast the roles of a corepressor and an inducer in negative regulation of an operon.
To compare: The functions of a corepressor and an inducer in negative regulation of an operon.
Introduction: Gene regulation is the process through which the cells control the expression of genes. It controls genes that are expressed to form a specific functional protein depending on the cell type. There are mechanisms that control gene expression at different levels.
Explanation of Solution
Operon contains coding DNA sequences, regulatory DNA sequences, and the regulatory proteins. Regulatory proteins act as both activators (TURN ON) and repressors (TURN OFF) of genes.
The similarities between corepressor and an inducer in negative regulation of an operon are as follows:
- Both are small molecules that bind to the repressor protein present in an operon, causing the repressor to change its shape.
The differences between the roles of a corepressor and an inducer in negative regulation of an operon are as follows:
Characteristics | Corepressor | Inducer |
Role in negative regulation of an operon |
A corepressor binds to the repressor protein, activates it to bind to the operator, and thereby inhibits transcription. For example, tryptophan acts as a corepressor in a trp operon. |
The binding of an inducer to the repressor protein makes it inactive and allows transcription of operon genes. For example, allolactose acts as an inducer in lac operon and binds to the lac repressor; hence, it cannot bind to the operator. |
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- Describe how the components of the trp operon system are affected by a mutation in trpC? Why is it that once enviornmental tryptophan is inserted into the cell, only the trp repressor is activated (turned on)?arrow_forwardUse the lac operon to describe the process of controlling transcription through operons (structural gene, operator (vs. promoter), inducer, repressor, regulatory gene)arrow_forwardIf you add a co-eepressor to a repressor protein and that allows it to bind the operator is this a inducible, constitutive or repressible operon?arrow_forward
- Draw a schematic diagram showing the components involved in the regulation of the tryptophan operon.arrow_forwardExplain how the trp operon is regulated by trp repressor and by attenuation.arrow_forwardFor the following types of transcriptional control, indicate whether the protein produced by the regulator gene will be synthesized initially as an active repressor or as an inactive repressor. Q. Negative control in a repressible operonarrow_forward
- You can determine the regulation of an unknown operon based on descriptions like those in the table below. For each row, choose whether the fact would suggest positive or negative or inducible or repressible regulation and indicate your answer with an X in the column. Only one X should appear in each row. In the presence of the signal, the structural genes are expressed. In the presence of the signal, the structural genes are not expressed. In the absence of the signal, the structural genes are expressed. In the absence of the signal, the structural genes are not expressed. The binding of the regulatory protein to the operon results in structural gene expression. The binding of the regulatory protein to the operon prevents structural gene expression. A mutation in the regulatory protein results in constitutive expression of the structural genes. A mutation in the regulatory protein results in no or low expression of the structural genes. Positive? Negative? Inducible? Repressible?arrow_forwardStudy the depiction of the lac operon in Figure 11.2. Normally, the genes are turned off when lactose is not present. Lactose activates the genes, which code for enzymes that enable the cell to use lactose. Mutations can alter the function of this operon. Predict how the following mutations would affect the function of the operon in the presence and absence of lactose: a. mutation of regulatory gene; repressor will not bind to lactose b. mutation of operator; repressor will not bind to operator c. mutation of regulatory gene; repressor will not bind to operator d. mutation of promoter; RNA polymerase will not attach to promoterarrow_forwardFor the following types of transcriptional control, indicate whether the protein produced by the regulator gene will be synthesized initially as an active repressor or as an inactive repressor. Q. Negative control in an inducible operonarrow_forward
- Biology (MindTap Course List)BiologyISBN:9781337392938Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. BergPublisher:Cengage Learning