text: In this step, two tagged adapters are ligated from 3’-dT-tails to 3’-dA-tails on both sides of double-stranded DNA library fragments. This process results in double-stranded library fragments that contain two random tags (α and β) on each side that are the reverse complement of each other (Figure 1 and 2). The "DNA: adapter" ratio is crucial in determining the success of ligation.