Comparisons of chicken, dog, and mouse genome sequence alignments to the human genome (http://www.ensembl.org) and Zoo-FISH data delineate an ancestral Amniota chromosome. Contiguous syntenic associations of human chromosome homologs 3 and 21 (top) are found in the genome sequence data indicated to the left of the human chromosome ideograms as well as in all of species analyzed by reciprocal Zoo-FISH. The vertical bars to the right of the G-banded human chromosome ideogram indicate the extent of the conserved segments displaying the syntenic associations in the selected species and chromosomes listed on top. Homologies to human chromosomes are identified by color: red (HSA3), blue (HSA21). Note that the intersection of homologous segments of human chromosome 3 in chicken, mouse, dog, and the horse (highlighted in yellow) indicate the ancestral fusion point of HSA3 to HSA21 in 3p12.3 (Froenicke 2005). Small genome alignment gaps inside conserved segments have been omitted for the sake of clarity. Similar agreements between chicken/human genome alignments and Zoo-FISH can be presented for the ancestral boreoeutherian associations HSA7/16, 14/15, and 16/19 (Supplemental Fig. 2). All three of these associations are missing in the bioinformatic model (Hillier et al. 2004; Bourque et al 2005).
