(a) Human and mouse synteny blocks. Every block corresponds to a rectangle, with a diagonal showing whether the arrangements of anchors in human and mouse (within the synteny block) are the same or reversed. (b) Combining anchors into clusters by the GRIMM-Synteny algorithm at G = 100 kb. The edges in the anchor graph connect the closest ends of the anchors. The anchors are color-coded by the resulting clusters. At G = 1 Mb, this forms a single cluster, which in turn forms a synteny block (thelower right block in the human 18/mouse 17 rectangle ina).