Error prevention and mitigation as forces in the evolution of genes and genomes

Why are short introns rarely a multiple of three nucleotides long? Why do essential genes cluster? Why are genes in operons often lined up in the order in which they are needed in the encoded pathway? In this Opinion article, we argue that these and many other - ostensibly disparate - observations are all pieces of an emerging picture in which multiple aspects of gene anatomy and genome architecture have evolved in response to error-prone gene expression.