Genomic and temporal distribution of duplicated genes in D. melanogaster. (a) The distance between duplicates does not increase sequentially with time, as estimated by dS values. The majority of gene pairs are either very near or far apart. The most frequent profiles for duplicated genes are (but not restricted to) consecutive (i-genes approximately 0) or recently (dS approximately 0) duplicated genes or both. Only pairs separated by up to 100 intervening genes and with dS < 5 are shown. (b) The proportion of pairs of duplicated genes that have separated increases over time, reaching a point where more than 90% of all duplicated genes are not physically linked. For example, there are 240 linked pairs in the dS 0-0.5 range, while there are only 19 for dS 4.5-5.0. The best fit exponential distribution that reaches a plateau at 92.51% is shown as a solid line.