Fig. 5: Persistent conservation of chromosomal features associated with microchromosomes in gnathostomes.

a Each proto-gnathostome chromosome, consisting of multiple segments, was mapped to modern genomes, and the total segment length in the human genome is shown on the x-axis, whereas the total segment length in the chicken, spotted gar and elephant shark genomes are shown on the y-axis. b Gene density (i.e., number of genes per megabase) was calculated in human, chicken, spotted gar and elephant shark segments derived from individual proto-gnathostome chromosomes. The x-axis shows the chromosome length in individual species. c Ohnologue density instead of gene density is shown on the y-axis.