FIGURE 1. Distribution of conserved blocks on the 33.5 Mb of human chromosome 21 (long arm).
From the following article:
Numerous potentially functional but non-genic conserved sequences on human chromosome 21
Emmanouil T. Dermitzakis, Alexandre Reymond, Robert Lyle, Nathalie Scamuffa, Catherine Ucla, Samuel Deutsch, Brian J. Stevenson, Volker Flegel, Philipp Bucher, C. Victor Jongeneel and Stylianos E. Antonarakis
Nature 420, 578-582(5 December 2002)
doi:10.1038/nature01251
a, Number of conserved sequence blocks identified (known and unknown) as a function of the threshold criteria for the size and percentage identity of the ungapped conserved blocks. b–d, The distribution of conserved blocks on the 33.5 Mb of human chromosome 21 at 
100 bp and 70% identity is shown. Histograms showing all 3,491 conserved blocks (b), 1,229 conserved blocks corresponding to known exonic sequences (c), and 2,262 conserved blocks of unknown function (d). Below the histograms, human chromosome 21 with its banding pattern, and with the corresponding mouse syntenic regions is shown (mouse chromosomes 16, 17 and 10 are indicated in blue, pink and green, respectively).