Practice question

If two restriction sites are placed at equal intervals on a linear DNA molecule, the terminal fragments flanking the central segment share identical length. Complete digestion yields three physical fragments, but two possess same molecular weight. In agarose gel, size determines migration, so fragments of equal length co-migrate and appear as one band with double intensity. Hence only two distinct bands are visible, and when intensity differences are overlooked or if both terminal fragments are exactly equal, gel interpretation may report as single band region. Equidistant symmetry causes band merging.