Different kinds of simulated permutations of gene positions applied to the Buchnera chromosome. Singletons are drawn in green whereas genes predicted to be in operons are drawn in red. 0: Original location of genes on the chromosome, 1: permutation preserving both rank and the spacing of the pTU to each other but modifying the rank of the genes between the pTU, 2: permutation preserving the rank but not the spacing between the pTU, 3: permutation of both the rank and the location of pTU, 4: gene positions on the chromosome randomly assigned.
Viñuelas et al. BMC Genomics 2007 8:143 doi:10.1186/1471-2164-8-143