Practice question

Restriction enzymes produce either cohesive sticky ends with 5' or 3' single-stranded overhangs or blunt ends where both strands are cut at same position symmetrically. EcoRI, HindIII, and XhoI leave 5' overhangs, facilitating directional ligation and preventing self-circularization. HaeIII recognizes GGCC and cleaves between G and C on both strands directly opposite, generating blunt termini lacking overhangs. Blunt-end ligation is less efficient requiring higher ligase concentration but allows joining of incompatible sites. Understanding end type predicts ligation efficiency, need for linker addition, and outcome of restriction mapping gels in cloning.