File:Fpls-02-00002-g004.png

English: Model for how duplicated genes come to possess different numbers of CNSs. A hypothetical example of how regulatory sequences of duplicate genes might evolve following whole genome duplication. The original whole genome duplication creates two homeologous copies of an ancestral gene, both of which evolve separately in two species, rice and sorghum that arose from the original tetraploid species. Red X's mark deleted sequences. Gray shapes represent intact regulatory elements which will not be identified as CNSs by comparing orthologous genes between species 1 and 2 because they are no longer shared between the two species. In this example, the genes located in subgenome A has retained more regulatory elements in both species than have the homeologous genes in subgenome B. As a result the genes in subgenome A possesses four orthologous CNSs, while the gene in subgenome B possess only three.