Practice question

Direct selection eliminates non-recombinant cells at plating stage based on genetic complementation or resistance, without need for secondary screening. Antibiotic resistance gene selection exemplifies this; only bacteria that have acquired plasmid bearing resistance gene such as AmpR survive on antibiotic-supplemented agar, directly selecting transformants. In contrast, blue-white screening requires visual inspection after growth, colony hybridization needs probe overlay and autoradiography, and replica plating is indirect technique transferring colonies between plates to infer phenotype, making them indirect screening procedures rather than immediate survival-based direct selection.