Synthesis errors in oligonucleotides are propagated into the genome by homology-directed repair.

Single-stranded oligonucleotides (ssODNs) are used as donor templates for gene editing by targeted endonuclease cleavage and homology directed repair (HDR). We probed their sequence fidelity by deep sequencing ssODNs from three manufacturers, and genomes derived from editing using these ssODNs as templates for HDR. The ssODNs carry single-nucleotide and small deletion synthesis errors in proportions differing widely among manufacturers; these are propagated into the genome by HDR; therapeutic gene correction strategies will need to this additional source of editing errors.