DNA only oligo spanning the sequence of the GFP sense strand (GFP.D)
was always more efficient at repairing the chromosomal DSB in
GFP than the complementary oligo comprising the GFP antisense
sequence (GFP.D comp) (Fig. 5). The bias did not depend on the
quality of the oligos, as it reproduced even with different oligo
preparations ordered from different companies (not shown). Moreover,
the bias was observed only when the oligos were correcting
the chromosomal broken GFP since no bias was revealed when the
same oligos (GFP.D and GFP.D comp) were correcting the broken
GFP on the plasmid (see below Section 3.4). It remains unknown
if the sense strand of the chromosomal GFP corresponds to the
lagging strand, as the GFP locus was randomly integrated in the
human genome and the site of integration was not determined
[21]. In light of the observed strand bias in the chromosomal targeting
by single-stranded DNA oligos,