Practice question

EcoRI recognizes GAATTC and HindIII recognizes AAGCTT, both cutting asymmetrically within the palindromic site to leave four-nucleotide 5' overhangs that are cohesive or sticky and complementary to themselves. When a DNA fragment is excised using these two different sticky-end cutters, each terminus retains its characteristic single-stranded extension derived from its own site. Self-ligation is prevented because ends are incompatible. Therefore the isolated insert carries two different sticky ends, one EcoRI-derived and one HindIII-derived, enabling efficient directional insertion into a similarly double-digested vector backbone during recombinant construction.