Final answer:
Negative control in gene regulation is when a repressor molecule binds to the DNA, inhibiting transcription. this is an example of how cells control gene expression to ensure that proteins are synthesized only when needed. The correct answer to the student's question is C) bound, and transcription is inhibited.
Step-by-step explanation:
When discussing gene regulation, a negative control refers to a mechanism by which a regulatory molecule inhibits gene expression. In the context of prokaryotic cells, negative control occurs when a repressor protein binds to the operator region of DNA, thereby preventing transcription. This occurs in cases like the trp operon, where abundant tryptophan causes the repressor to bind to the operator, inhibiting transcription.
Hence, a negative control can be defined as a condition where a regulator molecule is bound, and transcription is inhibited or, conversely, the regulator molecule is removed, which allows for transcription to start.Answering the student's question: negative control means a regulator molecule is bound, and transcription is inhibited (C).