Practice question

Circular DNA lacks free ends, forming a continuous loop. A single restriction cut converts the circle into a linear molecule of full length. Each additional cut divides one existing fragment into two. Consequently, in complete digestion the number of fragments generated equals exactly the number of recognition sites cleaved. With three distinct sites, three separate fragments appear whose sizes sum to the plasmid length. This contrasts with linear DNA where fragments are n+1. Understanding circular topology helps interpret plasmid mapping gels correctly during cloning validation experiments.