What is a DNA library in sequencing?

• A. A prepared collection of DNA fragments with sequencing adapters suitable for platform-specific sequencing
• B. A database of gene sequences
• C. A collection of proteins
• D. A single DNA fragment

Answer: (A)

The main idea is that a DNA library is a prepared collection of DNA fragments that have sequencing adapters attached, making them ready for the sequencing platform. The adapters provide the binding sites for sequencing primers and, in many technologies, enable attachment to the flow cell and amplification of each fragment. Library preparation typically involves fragmenting the DNA, polishing ends, ligating adapters, and often enriching the fragments by PCR so the sample can be read by the sequencer. This is why this option best fits: it describes a set of DNA pieces equipped with the platform-specific adapters needed for sequencing. It’s not just a database of sequences, not a collection of proteins, and not a single fragment.