A 7.5kb linear DNA fragment was cleaved with HindIII, Smal, and a combination of the two enzymes. HindIII cleaved the fragment into 2.5kb and 5kb pieces, Smal into 2kb and 5.5kb pieces, and the combined enzymes into 2.5kb, 3kb, and 2kb pieces. When the combined enzyme fragments were further digested with EcoRI, the 3kb fragment was lost and a 1.5kb fragment appeared, indicating an EcoRI cleavage site within the original 3kb fragment.