[De Novo Gene Birth].

According to classic ideas, new genes emerge from old genes by duplication or horizontal transfer. Analyses of a large number of genomes in recent decades have shown that some genes have no visible homologs and have presumably emerged de novo from previously noncoding sequences. The review considers possible mechanisms of de novo gene formation, the properties of protein sequences encoded by such genes, and features of their expression and selection. The problem of identification of de novo arising gene is discussed separately.