We have elaborated a method which has allowed us to estimate the direction of 
translocation of orthologs which have changed, during the phylogeny, their 
positions on chromosome in respect to the leading or lagging role of DNA 
strands. We have shown that the relative number of translocations which have 
switched positions of genes from the leading to the lagging DNA strand is lower 
than the number of translocations which have transferred genes from the lagging 
strand to the leading strand of prokaryotic genomes. This paradox could be 
explained by assuming that the stronger mutation pressure and selection after 
inversion preferentially eliminate genes transferred from the leading to the 
lagging DNA strand.