[The birth and death of genes]

Duplications of DNA regions with subsequent divergence of the duplicated copies by mutations is traditionally considered to be the major mechanism of the new genes appearance. After duplication, only a small fraction of the paralogs remains unchanged, while most copies are converted into pseudogenes or acquire new functions as a consequence of either subfunctionalization or neofunctionalization events. In some cases, certain regions of duplicated copies can combine with each other, giving rise to functionally new genes. Analysis of the primate genomes revealed a burst of segmental duplications in apes. It was demonstrated that some of these duplications include genes that are specifically duplicated only in human. Genome sequencing, followed by transcriptome analysis, enabled the identification of transcribed pseudogenes in mammalian genomes, that contradicts with the traditional view of pseudogenes as inactive copies of functioning genes.