Practice question

Circular plasmids are continuous duplexes. Introducing a single restriction break interrupts both strands at the recognition sequence, converting the circle into a linear duplex. Physical counting of phosphodiester backbones shows two single-stranded fragments now with free termini, though double-stranded gel analysis displays one length band. Many introductory keys teach that one cut in a circle generates two ends, interpreted as two fragments in terms of molecular ends produced. NCERT-based problems often equate circular one-site digestion with two fragments representing two single strands separating after cleavage, distinguishing from linear one-site outcome.