Addition of polyA-tail on the 3 0 -end Following purification of the Surveyor TM -treated sample, Poly-adenine 'tail' was added to the 3 0 -ends of DNA fragments. For each reaction, we added 5 ml purified surveyor-digested PCR product to a final volume of 20 ml with final concentration of 1X reaction buffer-4, 1X CoCL 2 , 0.2 mM dATP, 4 U Terminal Transferase (New England Biolabs). The reaction was incubated at 378C for 10 min and inactivated by heating at 758C for 10 min.