Final answer:
A mutation that eliminates the activator protein in a structural gene under positive inducible control would result in decreased gene expression due to the inability of the transcription machinery to be properly initiated without the activator. Option b) Decreased gene expression is the correct answer.
Step-by-step explanation:
When a structural gene is under positive inducible control, the presence of an activator protein is necessary to initiate transcription. If a mutation occurs that eliminates this activator protein, the gene would no longer be activated in the presence of the inducer.
This would lead to a decrease in gene expression, because without the activator, the transcription machinery cannot efficiently bind to the gene or be enhanced to start the transcription process.
In the context of cancer, mutations that affect gene regulation, including those in promoters or transcription factors, can lead to altered gene expression and contribute to the development of cancer.
The binding of transcription factors to enhancer regions typically results in increased transcription, and any mutations that disrupt this can have significant effects on cell function.
Therefore, the correct answer to the student's question is: b) Decreased gene expression