Orthoweb is a web based application for calculating phylostigraphic age index (PAI), divergency index (DI) and other characteristics of genes presented in gene networks. PAI defines the age of gene through the divergence time between the species under study and their most distantly related taxon in which a ortholog of the gene was found. DI shows the type of selection affecting the gene by analyzing the ratio of nonsynonymous and synonymous substitution in nucleotide sequences of gene and its orthologs.

The example of PAI calculation for H. sapiens gene with 6 orthologous genes found. PAI is the number of the taxon, most distant from the root of tree, common in lineage of H. sapiens and all species with orthologous genes found. In this example the PAI value is 9 corresponds to Euarchontoglires taxon.

More information is available in the guide.