Which statement best describes the role of arabinose in this system?

Which statement best describes the role of arabinose in this system?

• A. It activates transcription of the red fluorescent protein through the araC-regulated promoter.
• B. It inhibits transcription of the red fluorescent protein.
• C. It acts as the primary carbon source.
• D. It degrades plasmid DNA.

Answer: (A)

Arabinose acts as an inducer that triggers transcription from the araC-regulated promoter by binding to the AraC protein and changing its activity from a repressor to an activator. In the absence of arabinose, AraC sits on the promoter in a way that blocks transcription of the downstream red fluorescent protein. When arabinose is present, it binds AraC, the complex then promotes RNA polymerase binding and initiation, leading to expression of the red fluorescent protein. So arabinose specifically activates transcription rather than inhibiting it, and its role here isn’t as a primary carbon source or as a factor that degrades plasmid DNA.

Arabinose acts as an inducer that triggers transcription from the araC-regulated promoter by binding to the AraC protein and changing its activity from a repressor to an activator. In the absence of arabinose, AraC sits on the promoter in a way that blocks transcription of the downstream red fluorescent protein. When arabinose is present, it binds AraC, the complex then promotes RNA polymerase binding and initiation, leading to expression of the red fluorescent protein. So arabinose specifically activates transcription rather than inhibiting it, and its role here isn’t as a primary carbon source or as a factor that degrades plasmid DNA.