Fig. 1.

Detecting symmetric inversion bias. (A) Inversions in circular prokaryotic genomes can occur with varying degrees of symmetry in relation to the ori-ter axis (grey dotted line). The furthest away the inversion axis (orange dotted line) can be from the ori-ter axis is a quarter of the genome (0.25). (B, D, F) Symmetric inversions cause X-shaped patterns in pairwise MUMmer alignments, which can be hard to discern (D, F) but are revealed as symmetry hot and cold spots when displaying X_i,j (C, E, G). (H) Distribution of D scores for Proteobacteria with experimentally determined ori positions. The black line is the logspline density fit to the whole dataset, the grey lines are logspline density fits to random 40% jack-knifed samples to explore outsize influence of individual genome pairs. (I, J) X_i,j heat maps representing a case of simulated genome divergence by random (I) and symmetric and quasi-symmetric (J) inversions.