Figure 6.

De novo gene evolution. Genes can evolve de novo through several mechanisms. Transcription of protogenes (noncoding RNAs with open reading frames (ORFs), overlapping gene ORFs, intergenic regions) lead to ribosomal association and translation of the message. Translated peptides might confer a selective advantage through potential weak promiscuous activities. The mechanism described in the innovation–amplification–divergence (IAD) model would operate to increase the effectiveness of the protogenes through positive selection and promote the birth of novel genes. Some protogenes never make the transition to become selectively advantageous in the long run and become pseudogenized.