What is the purpose of sequencing adapters in a DNA library?

• A. To label proteins
• B. To allow platform-specific sequencing
• C. To degrade DNA
• D. To increase plasmid copy number

Answer: (B)

Sequencing adapters provide the essential binding and priming sites that let a DNA fragment be read by a sequencing instrument. They are ligated to both ends of DNA fragments in a library so the fragments can attach to the sequencing platform (for example, bind to a flow cell) and be amplified and sequenced. They also often include index sequences that enable multiplexing multiple samples in the same run and distinguishing them later. Because of this, adapters are specifically about enabling platform-specific sequencing rather than labeling proteins, degrading DNA, or increasing plasmid copy number.