Paralogous Genes (Molecular Biology)

Paralogous genes are two or more genes that emerged during evolution from a common ancestral gene by gene duplication within a species. Usually, they acquire different functions; well-known examples are the a and b-hemoglobin polypeptide chains and that of myoglobin. They contrast with orthologous genes, which have not been duplicated within a species, but retain the same function and have descended during evolution by the process of speciation only. Both orthologous and paralogous genes are homologous, but a comparison of paralogous genes from different species will not reflect the process of species divergence. Paralogous genes are usually present as members of a gene family within a genome. For more details, see Orthologous Genes.