Dissecting zebrafish development with microarray analysis. (a) Eight selected embryos ranging from the 16-cell to 8-somite stage. (b) Mean, unnormalized log2 signal intensities from microarray analysis (smooth bars, foreground signal and scatter board bars, background signal). (c) Principal component analysis (PCA) on unnormalized log2 ratio data (test/reference) showing a 'developmental' curve starting at the 16-cell stage and ending at the 8-somite stage. (d) Spearman correlations between the samples reflect the developmental distance.