FIG. 1.
OC as a quantitative measure of orthology between different types of protein categories. (A) In the case of a one-to-one correspondence between genes in two genomes, OC = 2No/(N1 + N2) where No is the number of orthologs and N1 and N2 are the numbers of members of the given protein family or functional category in the two compared genomes. (B) If there is a duplication (two or more members) in one or both of the species that occurred after divergence of the two species, then OC = (No1 + No2)/(N1 + N2) where No1 and No2 are the numbers of members in orthologous clusters from the two respective genomes.