Figure 1.

A simplified version of prokaryotic operon organization and functional linkages based on the Operon method. (a) Prokaryotic operon organization. Genes A, B, and C are transcribed together onto a single polycistronic transcript, which is then translated to produce three separate proteins. Proteins originating from genes of a common operon often have similar functions, interact physically through protein-protein interactions, or participate in shared biochemical pathways. (b) Functional Linkages based on the Operon method. Genes A, B and C are 'linked' if the intergenic nucleotide distance between pairs of adjacent genes is less than or equal to the specified threshold. In this case the distance between gene A and B, and the distance between gene B and C is less than the hypothetical distance threshold, thereby allowing links between all possible sets of genes.