Practice question

Isocaudomers are distinct restriction endonucleases that recognize different nucleotide sequences yet generate identical cohesive ends, permitting intermolecular ligation. XhoI recognizing 5'-C^TCGAG-3' and SalI recognizing 5'-G^TCGAC-3' represent classic example; both release fragments with 5' overhang TCGA. When such fragments are mixed, complementary ends anneal and are joined by ligase, forming CTCGAC or GTCGAG chimeras refractory to cleavage by either enzyme. Isocaudomer compatibility expands cloning flexibility, allowing insertion of a SalI fragment into XhoI-linearized vector when conventional sites are absent or preserved.