Model of T-nucleotide formation involving a putative error-prone DNA synthesis.

Several ends with 3′OH hydroxyl groups could possibly provide primers for polymerase extension: (1) One of the broken ends, either by a “snap-back” mechanism (eg, step A, intra-strand priming from D3.3 top strand) or by “strand invasion” (eg, step B, priming from J_H6, bottom strand); (2) template-directed capture of filler RNA/DNA, annealing in front of the copy.37