The chromosomal distribution of lamprey/chicken orthologs reveals conserved syntenic segments and paralogous chromosomes that derive from individual ancestral chromosomes. Lamprey linkage groups are oriented along the y-axis, and chicken chromosomes are oriented along the x-axis. Circles reflect counts of syntenic orthologs on the corresponding lamprey LG and chicken chromosome, with the size of each circle being proportional to the number of orthologous genes. The color of each circle represents the degree to which the number of observed orthologs deviates from null expectations under a uniform distribution across an identical number of LGs, chromosomes, and genes per LG and chromosome. Shaded regions of the plot designate homology groups that correspond to presumptive ancestral chromosomes, marked A–M (Supplemental Table S1). The ordering of lamprey LGs along the y-axis is provided in Supplemental Table S4.
