The evolutionary origin of orphan genes

Current models of gene evolution have concentrated on mechanisms that are mediated by duplication and by transposable elements, but these models have not yet fully evaluated the possibility of de novo evolution.Orphan genes with no homology to genes in other evolutionary lineages occur in all genomes and are candidates for the de novo evolution of genes.Several examples of de novo evolved genes have now been found, and the emergence process can involve a phase in which a gene functions as a non-coding RNA.Orphan gene emergence rates are elevated during adaptive radiations.Orphan gene emergence over time appears to be continuously high, but most of these newly emerged genes are likely to be subsequently lost.It is still an open question whether newly evolved genes can form new stable protein domains or whether they act as intrinsically unstructured proteins.The emergence of new genes may contribute to evolutionary novelties to the same degree as does the emergence of new regulatory interactions.