Fig. 6
From: Evolution of transcript structure and base composition of rDNA expansion segment D3 in ticks
Base substitutions capable of preserving (upper set of boxes) or establishing (lower set) complementary base pairing. The two middle rows represent bases (pairing or not) that are opposite each other in a stem. An ellipse in a box indicates that a mutation from the base in the row to the base listed above the column would result in a hydrogen-bonded pair.
