Figure 1. Length distributions of perfectly conserved sequences from natural genome alignments typically yield power laws, as shown in subfigure A for mouse/human alignment – provided that the genomes are not too closely-related, as illustrated by subfigure B the approximately exponential length distributions from chimpanzee/human alignment.

Relaxing the matching condition, so that A = G and C = T for example, yields substantially more aligned sequence, yet shapes that are very similar overall to those shown here [8], [33].