Gene cassette is:

Element Characteristic Role in spread of resistance genes Self transmissible plasmid Circular, autonomously replicating element; carries genes needed for conjugal DNA transfer Transfer of resistance genes; mobilization of other elements that carry resistance genes Conjugative transposon Integrated elements that can excise to form a non-replicating circular transfer intermediate; carries genes needed for conjugal DNA transfer Same as self-transmissible plasmid Mobilizable plasmid Circular, autonomously replicating element; carries gene that allows it to use conjugal apparatus provided by a self-transmissible plasmid Transfer of resistance genes Transposon Can move from one DNA segment to another within the same cell Can carry resistance genes from chromosome to plasmid or vice versa Gene cassette Circular, nonreplicating DNA segments containing only open reading frames; integrates into integrons Carry resistance genes Integron Integrated DNA segment that contains an integrase, a promoter, and an integration site for gene cassettes Forms clusters of resistance genes, all under the control of the integron promoter Ref: ANTIMICROBIAL AGENTS AND CHEMOTHERAPY. 1997; 41:2321-25