Activation-induced cytidine deaminase (AID) is believed to initiate somatic hypermutation (SHM) by deamination of deoxycytidines to deoxyuridines within the immunoglobulin variable regions genes. The deaminated bases can subsequently be replicated over. processed by base excision repair or mismatch repair. leading to introduction of different types of point mutations (G/C transitions. https://www.roneverhart.com/Bearbrick-WALL-E-400/