Practice question

Molecular linkers are blunt-ended synthetic double-stranded oligonucleotides containing one or more internal restriction sites. After ligation to blunt-ended target DNA with T4 DNA ligase, digestion with corresponding restriction enzyme exposes cohesive termini for cloning. Adaptors are asymmetric duplexes engineered with one blunt end and one pre-formed sticky end; they require no post-ligation restriction cleavage, as cohesive overhang is built in. Adaptors reduce risk of linker oligomerization and self-ligation, improving efficiency. Both strategies facilitate addition of new restriction sites and conversion of blunt fragments into insertable modules for plasmid construction.