The top 20 categories of duplicated genes were defined by a BlastClust analysis of a data set comprised of all duplicates. Duplicates were defined as having the best BLAST score of another gene within the same genome relative to genes within NR plus the other Frankia strains, Acidothermus, Kineococcus, and Streptomyces spp. with a maximum cutoff of 10⁻⁴.