Lengths of coding and noncoding regions of a gene correlate with gene essentiality and rates of evolution

Gene length correlates with the coding evolutionary rates of genes. Although the 'Hill-Robertson (HR) interference' model was suggested as an explanation for the correlation, we present an alternative explanation for the relationship between gene length and evolutionary rate. First, genes with longer coding sequences were significantly more essential and evolved more slowly than genes with shorter CDSs, and they contained more functional domains within the gene. Surprisingly, the same trends held for the lengths of other subcomponents; genes that carried longer 5' and 3' untranslated regions and introns were more essential. Additionally, the noncoding subcomponents that had higher densities of conserved sites were longer. Furthermore, the density of conserved sites in a coding region of a gene was associated with the density of conserved sites in the noncoding regions of that gene. Finally, in all five vertebrate species that were tested, more functionally constrained genes tended to carry longer subcomponents.