Cluster-graph representing a sample of 19 TB cases with six distinct genotypes. Each node represents a cluster of genotypically identical isolates, and the sizes of clusters are indicated inside the nodes. (A) Illustration from Tanaka and Francis (2005). The arrow indicates the sense of evolution through mutation events. (B) Our own representation. Dotted circles indicates mutation steps, with one mutation step between g1 and g3, but two between g1 and g4, for instance.