Clusters of gene expression profiles from a seven-point time course of mammary lactation and involution. Fifteen K means clusters of 4103 differentially expressed transcripts from seven stages of lactation and involution. Fourteen primary clusters (b) were grouped according to similarity into (a) seven basic profiles: Inv1, Inv2, Inv3, Inv4, Lac1, Lac2 and Lac3. These similar clusters were pooled and plotted as seven combined expression profiles. The 15th cluster represented differential expression between 5-day and 10-day lactation only (not shown). The number of genes for each pooled cluster is indicated to the right of panel A. The number of genes (brackets) and the cluster ID is indicated for each primary cluster in panel B. Each differentially expressed transcript is represented only once in the 15 primary clusters. The number of genes in each combined profile (panel A) is the sum of its primary profiles (panel B). Y-axis is the mean of normalized intensities. Error bars represent the standard error of the mean for all transcripts in each cluster. X axis = 7 point timecourse across lactation (Lac) and involution (Inv). Dotted lines highlight 10 day lactation and 24 hour involution timepoints.