Schematic representation of the gene duplication data sets employed in this study. (A) Prespeciation duplication set (Pre-SD), 35 families. (B) Postspeciation duplication set (Post-SD) with one duplication in mouse, 73 families. (C) Postspeciation duplication set (Post-SD) with one duplication in rat, 29 families. (D) Postspeciation duplication set (Post-SD) with one duplication in mouse and one in rat, 15 families. Black circles indicate a duplication event and grey circles a speciation event. Rn, Rattus norvegicus; Mm, Mus musculus; Hs, Homo sapiens; Bt, Bos taurus; Cf, Canis familiaris; Ec, Equus caballus; Fc, Felis catus.