The gene replica hypothesis, also known as the duplication-divergence model, describes the theory that new genes emerge through the duplication of existing genes, followed by mutations in the duplicates that create new functions. Synonyms for this idea include gene duplication theory, gene family expansion theory, and duplicate gene model. The concept has been extensively studied in evolutionary biology and has provided valuable insights into the microevolutionary mechanisms that drive the diversification and adaptation of species over time. Understanding the gene replica hypothesis is essential for elucidating the genetic basis of complex phenotypic traits, as well as for developing novel strategies to enhance genetic diversity and resilience in natural and engineered systems.