Practice question

Complete digestion means every recognition sequence is cleaved in every molecule. For linear DNA the general rule fragments = number of restriction sites + 1 applies because each cut subdivides one existing molecule. With zero sites, fragment count remains one uncut band. One site yields two, two sites yield three, thus three sites necessarily yield four fragments whose sizes correspond to distances between neighboring sites plus two terminal segments. Summation of fragment lengths must equal original molecule length, a key check during gel analysis and map assembly.