In eukaryotic cells, an expression vector typically contains what to drive gene expression?

• A. A prokaryotic promoter only
• B. A eukaryotic promoter and regulatory elements to drive gene expression in eukaryotic cells
• C. Only a bacterial origin of replication
• D. A replication origin and antibiotic resistance gene only

Answer: (B)

To drive gene expression in eukaryotic cells, the vector must include a promoter that is recognized by the host’s transcription machinery, along with regulatory elements that fine-tune expression. In eukaryotes, transcription is initiated by RNA polymerase II at a eukaryotic promoter, and nearby enhancers or other regulatory sequences help control how much, where, and when the gene is expressed. The vector often also contains features for proper mRNA processing, such as a polyadenylation signal, which further supports stable, mature transcripts.

A prokaryotic promoter wouldn’t recruit the eukaryotic transcription machinery, so it wouldn’t drive expression in eukaryotic cells. A bacterial origin of replication and antibiotic resistance gene are there to propagate and select the plasmid in bacteria, not to regulate transcription in eukaryotic cells, so they don’t accomplish expression in the target eukaryotic system.