Blunt-ended products are produced by Q5 High-Fidelity DNA Polymerase (and all Q5 product formulations). If needed for TA cloning , 3´A-overhangs can be added with a different polymerase. It is very important to remove all the Q5 High-Fidelity DNA Polymerase first by purifying the PCR product. The proofreading activity of Q5 is very strong, so any residual polymerase will degrade the A-overhangs as they are added. Taq DNA Polymerase or Klenow (exo-) DNA Polymerase are excellent options for A-overhang addition. We recommend ligating immediately so the 3´A-overhangs will not be lost during storage.