The PBAD promoter on the plasmid drives expression of which gene?

The PBAD promoter on the plasmid drives expression of which gene?

• A. It is the PBAD promoter that drives expression of the RFP gene
• B. It is the promoter for the gfp gene
• C. It binds a ribosome to start translation
• D. It is a terminator sequence

Answer: (D)

PBAD is a transcriptional promoter. Its role is to start transcription of the gene that sits downstream of it when the inducer (arabinose) is present. It does not encode a protein itself, nor does it tell the ribosome where to start translation—that’s a job for the ribosome binding site. It also isn’t a terminator sequence; terminators stop transcription downstream. Which gene is expressed under PBAD depends on what gene is placed immediately after the promoter in the plasmid (for example, GFP or RFP could be the downstream gene if that’s how the plasmid is arranged).

PBAD is a transcriptional promoter. Its role is to start transcription of the gene that sits downstream of it when the inducer (arabinose) is present. It does not encode a protein itself, nor does it tell the ribosome where to start translation—that’s a job for the ribosome binding site. It also isn’t a terminator sequence; terminators stop transcription downstream. Which gene is expressed under PBAD depends on what gene is placed immediately after the promoter in the plasmid (for example, GFP or RFP could be the downstream gene if that’s how the plasmid is arranged).