The origin of new genes: glimpses from the young and old
Key PointsThe variation in the numbers of genes in different organisms indicates a general process of the origin and evolution of new genes.Examining young genes is a direct approach to study this process, whereas ancient genes reveal the antiquity of some origination mechanisms.Several molecular mechanisms are involved in the creation of new gene structure, among which exon shuffling, retroposition and gene duplication have been found to be particularly important.A new gene in its early stage usually undergoes rapid changes in sequence, structure and expression, which indicates a continuous evolution of function.A significant role of positive Darwinian selection has been detected underlying these changes and adaptive evolution might have directed the entire origination process of new genes.Direct and indirect observations of new genes in eukaryotic genomes show that genes with new functions are not as rare as was previously thought.Analysis of the repeated new gene origination by retroposition in the Drosophila genome has uncovered a pattern in which new genes tend to avoid the X-chromosome linkage and most of the X-chromosome-derived autosomal new genes have evolved male-specific functions. This points to the importance of genome position in new gene origination.AbstractGenome data have revealed great variation in the numbers of genes in different organisms, which indicates that there is a fundamental process of genome evolution: the origin of new genes. However, there has been little opportunity to explore how genes with new functions originate and evolve. The study of ancient genes has highlighted the antiquity and general importance of some mechanisms of gene origination, and recent observations of young genes at early stages in their evolution have unveiled unexpected molecular and evolutionary processes.