Final answer:
Reversing the positions of the promoter and operator in an operon would disrupt gene regulation since the RNA polymerase may not bind properly, or its function may be obstructed by the repressor.
Step-by-step explanation:
If the positions of the promoter and operator were reversed in an operon, a disruption in gene regulation would occur. The promoter is the site where RNA polymerase binds to initiate transcription, and the operator is where a repressor protein can bind to prevent transcription.
By reversing their positions, the RNA polymerase may not properly recognize and bind to the promoter, or it might even bind but then get obstructed by the repressor bound at the operator, now incorrectly positioned upstream. Mutations in these regions can lead to various outcomes:
A mutation in the lac operon operator that prevents repressor binding would result in continuous transcription of the genes involved in lactose metabolism, even in the absence of lactose.
A mutation in the trp operon operator that prevents repressor binding would lead to nonstop synthesis of tryptophan-synthesizing enzymes, regardless of tryptophan levels.
Mutations in the promoter sequence can prevent RNA polymerase from attaching, leading to disrupted gene expression.
A mutation in a cell-surface receptor's intracellular domain would affect signal transduction, potentially changing or nullifying the signal response if it was switched with a domain from another receptor.
This could alter the function of the receptor and subsequently affect cellular behavior and processes.