Pattern Predicted for the Relative Locations of Paralogous Genes from Two Genome Duplications

<div><p>(A) Representation of a hypothetical genome that has 22 genes shown as colored squares.</p> <p>(B) A genome duplication generates a complete set of paralogs in identical order.</p> <p>(C) Many paralogous genes suffer disabling mutations, become pseudogenes, and are then lost. One could imagine this condition being evidence of a single round of genome duplication followed by significant gene losses.</p> <p>(D) A second genome duplication recreates another set of paralogs in identical order, with multigene families that retained two copies now present in four, and those that had lost a member now present in two copies.</p> <p>(E) Again, many paralogous genes suffer disabling mutations, become pseudogenes, and are then lost. Of course, unrelated gene duplications and transpositions can occur. Even though this leaves only a few four-member gene families, the patterns of 2- and 3-fold gene families unite, in various combinations, all four genomic segments, revealing that the sequential duplications had been of very large regions, in this case all or nearly all of this hypothetical genome.</p>