Cell-type specification coincides with major changes in transcriptome phenotype. The standardized mRNA abundance of genes involved in later development (y-axis) is plotted versus time (hours, x-axis). Data are from the filter development experiment. We grouped the genes based on general functional class or developmental process in which they are involved (A – D), as indicated above the panels. Legends above the panels indicate the gene names. The vertical axis scale varies to accommodate different levels of gene expression. Each data point represents the average of 2 independent biological replicates.