Gene duplication: A major force in evolution and bio-diversity

Abstract

Bridges reported one of the earliest observations of gene duplication from the doubling of a chromosomal band in a mutant of the fruit fly, Drosophila melanogaster, which exhibited extreme reduction in eye size. Based on whole-genome analysis of Arabidopsis thaliana, there is compelling evidence that angiosperms underwent two whole-genome duplication events early during their evolutionary history. Recent studies have shown that these events were crucial for the creation of many important developmental and regulatory genes found in extant angiosperm genomes. Recent studies provide strong indications that even yeast (Saccharomyces cerevisiae), with its compact genome, is in fact an ancient tetraploid. Gene duplication is providing new genetic material for mutation, drift and selection to act upon, the result of which is specialized or new gene functions. Without gene duplication, the plasticity of a genome or species in adapting to changing environments would be severely limited. The era of whole genome sequencing of model organisms suggests a number of duplication events take place while evolving modern species.

Imbalanced positive selection maintains the functional divergence of duplicated DIHYDROKAEMPFEROL 4-REDUCTASE genes

“…The maintenance of gene copies of floral characters is usually justified as neofunctionalization (neoF) and subfunctionalization (subF) driven by positive selection3. Although balancing selection was suggested as one of the mechanisms for the maintenance of divergent (neoF) or complementary (subF) functions of functional gene copies45, several studies indicated that positive divergent selection and duplication events act as reciprocal evolutionary forces driving adaptive trait diversification67. Flagel and Wendel8 suggested that unequal crossing-over and/or gene conversion would homogenize duplicates, providing a means of amplifying adaptively important genes, with a tendency to accelerate the divergence of non-recombining clusters, and permitted gene family diversification and evolutionary plasticity cf.…”

“…However, duplicated genes usually have only minor sequence variations that are sufficient to alter the substrate and product specificity but, thus, possess insufficient characteristics to predict their functional divergence1. On the other hand, both concerted evolution and purifying selection retained only small variations between paralogous genes for a long time, ensuring that the functional constraints of duplicated genes paralleled their expression in different tissues (i.e., subF)67.…”