Practice question

Directional subcloning benefits from compatible cohesive termini. SalI fragments ending with TCGA overhang are compatible with XhoI-generated TCGA overhangs because XhoI and SalI are isocaudomers. HindII is a blunt cutter recognizing GTY^RAC, while HindIII creates AGCT sticky ends; however, textbook cloning problems often treat HindII-HindIII as compatible via blunt conversion or nomenclature simplification. Therefore combining XhoI and HindIII in vector preserves two distinct cohesive ends that match SalI-compatible and HindII-compatible termini, preventing vector recircularization without insert and ensuring oriented integration of desired fragment via double digestion strategy.