What is a typical example of a selectable marker used in plasmids?

What is a typical example of a selectable marker used in plasmids?

• A. Fluorescent reporter gene.
• B. A promoter.
• C. Antibiotic resistance gene.
• D. Origin of replication.

Answer: (C)

Selectable markers are genes that let cells carrying the plasmid be distinguished by growth under selective conditions. An antibiotic resistance gene is the classic example: bacteria with the plasmid can survive on media containing the antibiotic, while cells without the plasmid cannot grow. This makes it easy to isolate transformed cells. A fluorescent reporter gene is great for visualizing expression but doesn’t by itself enable survival-based selection. A promoter just controls when a gene is turned on, not survival, and the origin of replication is needed for plasmid copying but doesn’t provide a growth advantage under selection. So the antibiotic resistance gene is the typical selectable marker.

Selectable markers are genes that let cells carrying the plasmid be distinguished by growth under selective conditions. An antibiotic resistance gene is the classic example: bacteria with the plasmid can survive on media containing the antibiotic, while cells without the plasmid cannot grow. This makes it easy to isolate transformed cells. A fluorescent reporter gene is great for visualizing expression but doesn’t by itself enable survival-based selection. A promoter just controls when a gene is turned on, not survival, and the origin of replication is needed for plasmid copying but doesn’t provide a growth advantage under selection. So the antibiotic resistance gene is the typical selectable marker.