Introns certainly impose a huge energetic burden to the cell, considering that the density of introns (i.e., the genic regions consuming large amounts of energy for nothing in terms of protein synthesis) is greater than that of exons in genomes. The reasons that introns propagated in some eukaryotic genomes regardless of this energetic disadvantage have been issues yet to be explained. According to Lynch [9], introns are just selfish DNAs that invade protein-coding genes in eukaryotic genomes, and the deleterious introns can be sustained due to severe population bottlenecks. Many studies have discussed selective advantages that introns bring to the cell in eukaryotes, contributing to overcoming the energetic disadvantage [21011121314151617181920]. However, the results derived from different studies are still controversial so far [132122232425].
