Genes within a single genome can be classified as singletons, dispersed duplicates, proximal duplicates, tandem duplicates and segmental/WGD duplicates depending on their copy number and genomic distribution. The following procedure is used to assign gene classes: (i) All genes are initially classified as ‘singletons’ and assigned gene ranks according to their order of appearance along chromosomes; (ii) BLASTP results are evaluated and the genes with BLASTP hits to other genes are re-labeled as ‘dispersed duplicates’; (iii) In any BLASTP hit, the two genes are re-labeled as ‘proximal duplicates’ if they have a difference of gene rank<20 (configurable); (iv) In any BLASTP hit, the two genes are re-labeled as ‘tandem duplicates’ if they have a difference of gene rank = 1; (v) MCScanX is executed. The anchor genes in collinear blocks are re-labeled as ‘WGD/segmental’. So, if a gene appears in multiple BLASTP hits, it will be assigned a unique class according to the order of priority: WGD/segmental>tandem>proximal>dispersed.