Signaling molecules that interact with repressor proteins to determine if a gene will be expressed:
A. Initiation regulation
B. Negative gene regulation
C. Positive gene regulation
D. Promotor gene regulation
The correct answer and explanation is:
The correct answer is B. Negative gene regulation.
Negative gene regulation refers to the mechanism where signaling molecules interact with repressor proteins to inhibit the expression of a gene. In this process, the repressor proteins bind to the operator region of the gene or operon, preventing the transcription machinery from accessing the gene. This effectively “turns off” gene expression.
In bacteria, an example of negative gene regulation can be observed in the lac operon. When the repressor protein is bound to the operator, the gene for lactose metabolism is not transcribed. However, when lactose (the signaling molecule) is present, it binds to the repressor, causing it to undergo a conformational change. This change prevents the repressor from binding to the operator, thus allowing the gene to be transcribed and the lactose to be metabolized.
This type of regulation is crucial for cells to conserve energy and resources. If a gene is continuously expressed when its product is not needed, it can result in unnecessary metabolic expenditure. Negative regulation, therefore, helps the cell adapt to changing environments by controlling when and how genes are expressed.
In contrast, positive gene regulation involves the interaction of signaling molecules with activator proteins to enhance gene expression. Initiation regulation typically refers to the control of transcription initiation, but it does not specifically address the interaction with repressor proteins. Promoter gene regulation refers to control mechanisms that influence the initiation of transcription but does not exclusively involve repressor proteins.