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Where do new genes come from? That's the question a team of biological sciences researchers from the U of A set out to answer in a new study.

They did so by examining the evolution of antifreeze proteins in fish鈥攁n essential adaptation that allows fish to survive in freezing waters by preventing ice formation through the binding of their antifreeze proteins to ice crystals.

The team investigated these proteins in three unrelated fish lineages and uncovered surprising results. While the proteins in each lineage are functionally and structurally similar, they evolved independently from different genetic sources.

This phenomenon, known as convergent evolution, represents a rare case of protein sequence convergence. It demonstrates how the same adaptive traits鈥攁nd even nearly identical protein sequences鈥攃an be produced through entirely different evolutionary trajectories.

The study provides concrete examples of different evolutionary mechanisms that can lead to the birth of new genes. Findings suggest that new genes can form by repurposing fragments of ancestral genes while incorporating entirely new coding regions (the protein-coding parts of the DNA).

This innovative concept bridges the gap between entirely new gene formation from noncoding regions and the more traditional model in which new functions can arise from duplicated genes.

The study, "Diverse origins of near-identical antifreeze proteins in unrelated fish lineages provide insights into evolutionary mechanisms of new gene birth and protein sequence convergence," was in Molecular Biology and Evolution.

Co-authors included Nathan Rives, Vinita Lamba, C-H Christina Cheng and Xuan Zhuang. The co-first authors, Rives and Lamba, are Ph.D. students in the Zhuang Lab at the U of A, which is led by assistant professor of biological sciences Xuan Zhuang, who oversaw the study. Cheng is a professor in the School of Integrative Biology at the University of Illinois Urbana Champaign.

The group's work also introduces a new model that advances understanding of the mechanisms behind new gene evolution: Duplication-Degeneration-Divergence. This model explains how new gene functions can arise from degenerated pseudogenes鈥攆ormerly functional genes that lost their original role.

This model also highlights how genes that appear to be nonfunctional or "junk" can evolve into something entirely new, a concept that holds significant implications for understanding adaptation under extreme environmental stress.

In the context of molecular evolution, this work represents a significant step forward in understanding how new genes are born and evolve, offering fresh perspectives on functional innovation鈥攐r gene recycling and adaptation.