What does the araC gene code for on the pARA-R plasmid?

What does the araC gene code for on the pARA-R plasmid?

• A. rfp
• B. araC protein (always being transcribed and translated)
• C. ampr
• D. pbad promoter

Answer: (B)

The main idea here is understanding what the AraC gene produces to control the arabinose-inducible system. The araC gene codes for the AraC regulatory protein, which sits at the center of the pBAD control system. AraC acts as a sensor and switch: in the absence of arabinose, it binds DNA in a way that keeps transcription off; when arabinose is present, AraC binds it and changes shape to recruit RNA polymerase, turning on transcription from the pBAD promoter. On the pARA‑R plasmid, this regulatory protein needs to be present so genes placed under the pBAD promoter can be expressed in response to arabinose. The other items listed aren’t the coding product of araC—the red fluorescent protein would be a reporter, ampicillin resistance is a separate marker, and the pBAD promoter is the regulatory sequence, not a gene that encodes a protein.

The main idea here is understanding what the AraC gene produces to control the arabinose-inducible system. The araC gene codes for the AraC regulatory protein, which sits at the center of the pBAD control system. AraC acts as a sensor and switch: in the absence of arabinose, it binds DNA in a way that keeps transcription off; when arabinose is present, AraC binds it and changes shape to recruit RNA polymerase, turning on transcription from the pBAD promoter. On the pARA‑R plasmid, this regulatory protein needs to be present so genes placed under the pBAD promoter can be expressed in response to arabinose. The other items listed aren’t the coding product of araC—the red fluorescent protein would be a reporter, ampicillin resistance is a separate marker, and the pBAD promoter is the regulatory sequence, not a gene that encodes a protein.