631190-10-30P AID: 2498 | 21/08/2015
Selectable marker is an antibiotic resistant gene present in a plasmid vector that is required for the selection of the bacteria transformed with that plasmid.
Selectable marker renders the bacteria the ability to survive in a growth medium after the addition of the appropriate antibiotic, and the other bacterial cells that do not contain the plasmid will die. Thus, a selectable marker allows the researcher to isolate only bacteria containing cloned plasmid.