Hierarchical clustering of MLL-AFF1 cases using top 100 SD probe sets. The top 100 probe sets, ranked by SD, were used to cluster the 48 MLL-AFF1 cases. The yellow bar indicates the branch point defining the 2 major cluster patterns. These patterns are named after the family of homeobox genes most commonly and highly expressed by its members (IRX or HOXA). Samples are shown in columns and probe sets are in rows. Captions across the right indicate the positions of some of the more conserved genes across a cluster. Increasing (red) or decreasing (green) gene expression is shown relative to the median (black) for each gene.