Single-molecule sequencing by hybridization. (a) A 31-nt target DNA is recoded by an 8-nt sequence A8, T8, G8 and C8 to yield a 248 bps fragment which is then ligated to form a 295 bps hairpin (see Methods). (b) To sequence the recoded hairpin we successively hybridize its open state with the coding oligonucleotides. The histogram of the hairpin blockage during rehybridization at Ftest is presented for each oligonucleotide: A8 (orange), T8 (green), G8 (red) and C8 (blue), while the full extension of the molecule at Ftest is shaded in grey.