Principal component analysis of expressed genes at differing stages of human terminal erythroid differentiation. (A) Samples representing 3 biologic replicates from individual stages of terminal erythroid differentiation clustered closely together. This tight clustering indicates that samples from each stage are very closely related and that the different stages of terminal erythroid differentiation are distinct. (B) Pairwise comparisons of replicates in scatterplot representation. Pearson correlations between pairwise comparisons using median expression of replicates from each differentiation stage. (Upper-right) The Pearson correlation values of genes with greater than 10 counts per million reads. (Lower left) Scatter plot data of log 2 counts per million reads for each gene of 1 sample compared with another. (Middle) Histograms of the log counts per million for each sample. The axis labels represent the log counts per million for the scatter and histogram plots. The y-axis for the histogram plots is scaled by the maximum y value. Baso, basophil; Ortho, orthochromatic; PC, principal component; poly, polychromatic; Pro E, proerythroblast.