Which plasmid feature initiates transcription of the inserted gene?

Which plasmid feature initiates transcription of the inserted gene?

• A. Ori
• B. Promoter
• C. Antibiotic resistance gene
• D. Terminator sequence

Answer: (B)

Transcription begins at a promoter. The promoter is a DNA sequence that RNA polymerase recognizes and binds to in order to start making RNA. In plasmid-based gene expression, the inserted gene will be transcribed only if a promoter sits upstream of it in the correct orientation and is capable of driving transcription. The promoter effectively tells the cell, “start here,” and can also control how strongly and under what conditions transcription occurs (for example, with inducible promoters that respond to a molecule like lactose or arabinose). Other features don’t initiate transcription: the origin of replication (Ori) is about copying the plasmid, the antibiotic resistance gene is used to select cells that carry the plasmid, and the terminator sequence signals where transcription ends, not where it begins.

Transcription begins at a promoter. The promoter is a DNA sequence that RNA polymerase recognizes and binds to in order to start making RNA. In plasmid-based gene expression, the inserted gene will be transcribed only if a promoter sits upstream of it in the correct orientation and is capable of driving transcription. The promoter effectively tells the cell, “start here,” and can also control how strongly and under what conditions transcription occurs (for example, with inducible promoters that respond to a molecule like lactose or arabinose).

Other features don’t initiate transcription: the origin of replication (Ori) is about copying the plasmid, the antibiotic resistance gene is used to select cells that carry the plasmid, and the terminator sequence signals where transcription ends, not where it begins.