Practice question

Selectable markers confer a growth advantage under selective conditions, permitting only transformed cells to propagate. Ampicillin resistance gene bla encoding β-lactamase hydrolyzes the β-lactam ring of ampicillin, allowing Escherichia coli harboring plasmid to grow on ampicillin-containing medium. Non-transformed cells are eliminated. LacZ, GFP, and luciferase are scorable or reporter markers that produce color, fluorescence, or luminescence for visual screening but do not provide survival selection. Thus antibiotic resistance genes remain the primary selectable markers for plasmid maintenance and clone isolation.