What is a typical method of DNA library preparation for NGS?

To prepare DNA for short-read sequencing, it's first fragmented into smaller pieces since short-read sequencing technologies like Illumina's can't handle long DNA strands. These fragments are then polished at the ends, typically by adding a single adenine base to create an overhang. Adapters, which contain barcode sequences for sample identification and sequencing compatibility, are then attached to the ends of the DNA fragments. These adapters serve multiple purposes: they help bind the DNA to the sequencing platform, and ensure compatibility with the specific sequencing technology. Optionally, the DNA libraries can be amplified through PCR to increase the amount of DNA available for sequencing. Following amplification, any leftover small fragments and oligonucleotides are removed to ensure the accuracy of the sequencing results. This cleanup step can be done using magnetic beads or spin columns.