Which statement correctly describes the purpose of antibiotic resistance markers in plasmids?

Which statement correctly describes the purpose of antibiotic resistance markers in plasmids?

• A. To select for cells that have taken up the plasmid
• B. To kill all bacteria that do not take up the plasmid
• C. To increase transformation efficiency
• D. To show a visible color change

Answer: (A)

Antibiotic resistance markers serve as a selection tool after introducing a plasmid. When cells are grown on media containing the matching antibiotic, only those that have taken up and maintained the plasmid with the resistance gene survive. This makes it easy to identify which cells carry the plasmid, separating transformed cells from those that didn’t acquire it. The marker doesn’t increase the likelihood of uptake, and it isn’t meant to create a visible color change—that’s the job of a separate reporter gene. In short, the marker’s purpose is to select for cells that have taken up the plasmid.

Antibiotic resistance markers serve as a selection tool after introducing a plasmid. When cells are grown on media containing the matching antibiotic, only those that have taken up and maintained the plasmid with the resistance gene survive. This makes it easy to identify which cells carry the plasmid, separating transformed cells from those that didn’t acquire it. The marker doesn’t increase the likelihood of uptake, and it isn’t meant to create a visible color change—that’s the job of a separate reporter gene. In short, the marker’s purpose is to select for cells that have taken up the plasmid.