What is a next-generation sequencing (NGS) library?

A next-generation sequencing library, which needs to be prepared before sequencing, consists of DNA fragments that have adapters fused to the 5’ and 3’ ends.

Preparing an NGS library involves fragmenting DNA through either physical, enzymatic, or chemical means, then sizing the fragments based on the optimal insert size, which depends on the sequencing application used. After having adapters attached to each end, the fragments are sized again using either agarose gel or a magnetic bead-based method. The library product is then quantified using a method such as qPCR (quantitative PCR).