Evolutionary relationship between genes:
- Orthologs: Two copies of the same gene in two different species
produced by speciation from a common ancestor.
- Paralogs: Two tandem copies of the same gene in the same genome due
to a gene duplication event.
- Xenologs: Horitzontal transfer of genetic material between two species
separated by a long evolutionary distance.
- Analogs: Two different genes from separated species that have converged
on the same function by separate evolutionary paths.