Sequencing By Ligation with Endonuclease V Digestion. 1) Sequencing the fourth base in the template tag, by using standard SBL with a Query Oligo that contains a Deoxyinosine (I). 2) Endonuclease V will recognize the Deoxyinosine and cleave the second phosphate bond towards the 3' end. The picture has white light background to make the bead visible as all fluorescence is ablated. 3) Repeat SBL to obtain the next positions.