Base editing Adenine Base Editing A genetic engineering technique that allows for the precise conversion of an A-T base pair to a G-C base pair in the genome. This technique uses a Cas9 nickase or catalytically impaired Cas9 fused to an evolved tRNA adenosine deaminase (TadA) enzyme that mediates the conversion of adenine to inosine, which is then trated as guanosine by the cellular DNA repair and replication machinery.