Practice question

Adapters are short, chemically synthesized double-stranded oligonucleotides designed to add desired cohesive termini to blunt-ended DNA. Each adapter is pre-formed duplex carrying one blunt end for ligation to target and one pre-formed sticky end that does not require subsequent digestion. After blunt ligation, the fragment acquires ready-to-clone overhangs. This contrasts with linkers that are blunt duplexes containing internal restriction sites needing cleavage. Adapters prevent concatemerization risks associated with linker digestion and allow direct conversion of blunt PCR products or sheared DNA into sticky-ended molecules for vector insertion.