The box-plot shows the distribution of genomic purine stretches consisting of 10 bp or more in prokaryotic phyla. The expected genomic fraction of RR-stretches is 0.001 (0.1%). The Actinobacterial and β-Proteobacterial groups were the only ones found to be underrepresented in terms of genomic RR-stretches.
Bohlin et al. BMC Genomics 2009 10:346 doi:10.1186/1471-2164-10-346