Final answer:
The statement about arabinose binding to AraC and promoting transcription of the arabinose operon is true. Ara C serves as an activator when bound to arabinose, enhancing transcription by changing its conformation and affinity for DNA near the promoter.
Step-by-step explanation:
The statement about the regulation of the arabinose operon is true. When arabinose is present, it binds to the protein Ara C, which in turn binds to the initiator site to promote transcription. The Ara C protein acts as an activator in the presence of arabinose, changing its conformation, and decreasing its affinity for the DNA site near the promoter that would otherwise repress transcription. Ara C is a positive regulator that, when bound to arabinose, allows RNA polymerase to access the promoter and initiate transcription of the arabinose operon.
This inducible control mechanism is similar to that of the lac operon, where the presence of lactose and the absence of glucose together induce transcription. CAP, stimulated by low glucose levels and bound cAMP, binds to the promoter to enhance the binding of RNA polymerase and induce transcription of genes necessary for lactose processing. Mutated promoters can alter the binding of transcription factors like Ara C or CAP, affecting transcription rates or potentially halting transcription.