A disease-linked, spontaneous, congenital [kon-GEH-nih-tul] germ line mutation creates a restriction site for HaeIII [HAY-three]. A diagnostic test for this mutation involves restriction digestion with endonuclease [en-doh-NEW-klee-ase] HaeIII. If the DNA of a patient with this mutation is tested and imaged using an agarose [AH-gah-rohs] gel, which of the following is expected?