Fig. 1. Hierarchical clustering of single-cell cDNAs and definition of clusters. Cluster dendrograms showing the results from (A) SigABC genes (probe sets significantly different across Groups A, B and C; n=114 probe sets; see Table S1 in the supplementary material) and (B) `Over-20 copies' probe sets (probe sets for which at least one of the 70 cDNA samples showed an expression level of >20 copies per cell; n=10493 probe sets). The dendrogram in A defines four clusters. In both dendrograms, each sample name represents one cell, and its color indicates the cluster to which it belongs. The first letter of the name indicates the cell group; for example, A-11L is a Group A cell. The values in red at the branches are AU (approximately unbiased) P-values (%) that indicate how strongly the cluster is supported by the data. For example, for a cluster with an AU P-value >95%, the hypothesis that `the cluster does not exist' is rejected with a significance level of 5%. The horizontal branch length represents the degree of dissimilarity in gene expression among the samples.