(A) Reconstructed karyotype of the Boreoeutheria ancestor (BEA) and its conservation in the chicken genome. The ancestral karyotype is based on comparative chromosome painting data from >80 eutherian species (Richard et al. 2003; Yang et al. 2003; Robinson et al. 2004; Wienberg 2004; Froenicke 2005). Each ancestral chromosome is named according to its orthologous segments in the human genome. The homologies of individual conserved segments to human chromosomes are identified by individual colors and numbers to the right of the ideograms. The degree of synteny conservation of the largest conserved segments in the chicken genome (http://www.ensembl.org) is indicated by gray bars to the left of the ideograms. For the precise homologies of the conserved segments 4a, 4b, 7a, 7b, 12a, 12b, 22a, and 22b see Froenicke (2005). The association of HSA10p to HSA12a is a comparatively weakly supported ancestral chromosome form as indicated by the dotted line, the scissor symbol, and the question mark. (B) Reconstructed karyotype of the ancestral rodent genome (RA). The reconstruction is based on recent comparative squirrel genome maps (Li et al. 2004); the Zoo-FISH data reviewed in Froenicke (2005); and on alignments of mouse, rat, and human genome sequences (http://www.ensembl.org). The association of human chromosomes 3 and 19 has been included according to yet-unpublished studies of representatives of two additional rodent suborders (A.S. Graphodatsky, F. Yang, L. Biltueva, T. Li, S. Romanenko, P. Perelman, N. Serdukova, E. Nevo, E. Ivanitskaya, T.J. Robinson, et al., in prep.). The nomenclature is the same as used in A. The boundaries of orthologous segments of human chromosome 3 are defined as: 3a: 3pter–3p25.1, 3p14.1–p12.3, 3q21.2–21.3; 3b: 3p25.1–3p14.1, 3q21.3–q24; 3c: 3p12.3–3q21.2, 3q24–qter.
