Practice question

De novo gene birth describes emergence of novel protein-coding genes from previously non-coding DNA rather than duplication or horizontal acquisition. Intergenic regions, antisense transcripts or intronic sequences acquire mutations creating open reading frame, transcription factor binding sites and translation signals. Phylostratigraphy reveals young lineage-specific genes initially disordered, moderately expressed, evolving under purifying selection after gaining function. Examples in yeast, Drosophila and mammals involve emergence from non-coding RNA that becomes stably translated. This mechanism expands proteome innovatively beyond modifications of ancestral genes.