Practice question

XhoI and SalI share identical cohesive termini despite differing recognition hexamers, classifying them as isocaudomers. XhoI cleavage of C^TCGAG and SalI cleavage of G^TCGAC both leave 5' overhang TCGA that readily anneals via complementary base pairing. Consequently, a vector digested with XhoI possesses compatible ends for an insert excised with SalI, and ligation by T4 DNA ligase generates a stable recombinant molecule. Preservation of phosphorylation on insert ends remains essential. The hybrid site CTCGAC is not efficiently recut, confirming successful insertion orientation.