Practice question

Double digestion with two enzymes should release an insert if both sites flank it, producing two bands typically insert and vector backbone. Observing only two bands of 7 kb and 3 kb summing to 10 kb total indicates that both enzymes cut efficiently at their unique sites, releasing fragments of expected sizes. Absence of additional intermediate bands or uncut supercoiled forms signifies complete reaction rather than partial cleavage. Circular DNA alone would show one linearization band, symmetric sites would show one size. The pattern confirms successful full digestion.