Practice question

Plasmids are accessory genetic elements replicating independently of main chromosome through own origin of replication compatible with host initiation factors. Typically circular double-stranded DNA of few kilobases to over 100 kb, encoding antibiotic resistance, virulence, catabolic pathways or conjugation machinery, they are dispensable under non-selective conditions and may be lost without lethal effect. Found predominantly in bacteria, also in some archaea and eukaryotes. Classification by incompatibility groups and mobilization ability underlies biotechnology vectors derived from natural plasmids like pSC101 and pUC for cloning and expression.