Practice question

Colony hybridization, developed by Grunstein and Hogness, identifies recombinant clones harboring specific DNA sequences without phenotypic screening. Colonies are replica-transferred to nitrocellulose or nylon membrane, lysed with alkali, and DNA denatured and fixed. The membrane is then incubated with a 32P or 35S labeled nucleic acid probe complementary to desired insert. After stringent washing to remove non-specific binding, positive colonies are detected by autoradiography where hybridization signal exposes X-ray film. Blue-white screening and direct antibiotic selection do not employ radioactive probes for sequence-specific detection.