A-overhang

Adenylation of blunt-ended DNA fragments enables you to create a binding site for a specific adapter to any DNA strand. Adenylation of a blunt-ended DNA results in a 3' end Adenine (A) overhang, and as you remember, Adenine pairs up specifically with Thymine.

The adapters have thymine at the 3' end that will specifically bind to the 3' adenine of the DNA sample.

A non-proofreading polymerase such as Taq could be used to add an adenine at the 3' of the blunt end DNA.

At the top are two horizontal gray lines, illustrating blunt DNA. The left end of the first line is marked as the 5' end and the right end is marked as the 3' end. On the second line are the ends reversed, with the 3' end to the left and the 5' end to the right. Beneath them are another set of identical gray lines, but with a blue arrow illustrating how adenine is added at the 3' end of the blunt DNA. Adenine is marked on both gray lines as a green A

Figure 1. A-overhang