Figure 4.

Functionally complex genes have more intergenic DNA than functionally simple genes. A comparison of intergenic distances among genes of different GO groups. The mean and median amounts of flanking intergenic DNA are shown for various functional categories of genes in (a) D. melanogaster and (b) C. elegans (black points and bars indicate mean value ± standard error; red bars indicate median values, red boxes enclose 25th-75th percentiles). Genes with low regulatory complexity are represented by the CDY, general RNA polymerase II (PolII) transcription factors, ribosomal components, metabolism, and housekeeping gene sets. Genes of high regulatory complexity are represented by receptor activity, cell differentiation, genes involved in embryonic development, genes involved in pattern specification, and specific RNA PolII transcription factors. All sets of low regulatory complexity have significantly less flanking intergenic DNA than all sets of high regulatory complexity regardless of species (Tukey-Kramer HSD, α = 1 × 10^-4).