Figure 4.

Schematic illustration of the hairpin primers and the spotting layout of the slides. A) The variable positions in the template part are marked as Z for the first template nucleotide and as Q for the second. The variable positions immediately after the 3′-terminus are marked as X and Y for the first and second nucleotide to be incorporated, respectively. B) Each of the 16 oligonucleotides is applied on the slide in four spots arranged on the grid in squares. In a column (vertically), all the four squares encode the same base for the first incorporation event (X). Each square within a row (horizontally) encodes one of the four nucleotides for the second incorporation event (Y).